Mercurial > hg > graal-compiler
view src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp @ 1022:4c3458a31e17
6888316: G1: has_aborted() || _cm->region_stack_empty() fails
Summary: Remove incorrect guarantee.
Reviewed-by: apetrusenko, iveresov
author | tonyp |
---|---|
date | Wed, 07 Oct 2009 09:42:18 -0400 |
parents | 0fbdb4381b99 |
children | e018e6884bd8 |
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/* * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, * CA 95054 USA or visit www.sun.com if you need additional information or * have any questions. * */ # include "incls/_precompiled.incl" # include "incls/_compactibleFreeListSpace.cpp.incl" ///////////////////////////////////////////////////////////////////////// //// CompactibleFreeListSpace ///////////////////////////////////////////////////////////////////////// // highest ranked free list lock rank int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3; // Constructor CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr, bool use_adaptive_freelists, FreeBlockDictionary::DictionaryChoice dictionaryChoice) : _dictionaryChoice(dictionaryChoice), _adaptive_freelists(use_adaptive_freelists), _bt(bs, mr), // free list locks are in the range of values taken by _lockRank // This range currently is [_leaf+2, _leaf+3] // Note: this requires that CFLspace c'tors // are called serially in the order in which the locks are // are acquired in the program text. This is true today. _freelistLock(_lockRank--, "CompactibleFreeListSpace._lock", true), _parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1 "CompactibleFreeListSpace._dict_par_lock", true), _rescan_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord * CMSRescanMultiple), _marking_task_size(CardTableModRefBS::card_size_in_words * BitsPerWord * CMSConcMarkMultiple), _collector(NULL) { _bt.set_space(this); initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle); // We have all of "mr", all of which we place in the dictionary // as one big chunk. We'll need to decide here which of several // possible alternative dictionary implementations to use. For // now the choice is easy, since we have only one working // implementation, namely, the simple binary tree (splaying // temporarily disabled). switch (dictionaryChoice) { case FreeBlockDictionary::dictionaryBinaryTree: _dictionary = new BinaryTreeDictionary(mr); break; case FreeBlockDictionary::dictionarySplayTree: case FreeBlockDictionary::dictionarySkipList: default: warning("dictionaryChoice: selected option not understood; using" " default BinaryTreeDictionary implementation instead."); _dictionary = new BinaryTreeDictionary(mr); break; } splitBirth(mr.word_size()); assert(_dictionary != NULL, "CMS dictionary initialization"); // The indexed free lists are initially all empty and are lazily // filled in on demand. Initialize the array elements to NULL. initializeIndexedFreeListArray(); // Not using adaptive free lists assumes that allocation is first // from the linAB's. Also a cms perm gen which can be compacted // has to have the klass's klassKlass allocated at a lower // address in the heap than the klass so that the klassKlass is // moved to its new location before the klass is moved. // Set the _refillSize for the linear allocation blocks if (!use_adaptive_freelists) { FreeChunk* fc = _dictionary->getChunk(mr.word_size()); // The small linAB initially has all the space and will allocate // a chunk of any size. HeapWord* addr = (HeapWord*) fc; _smallLinearAllocBlock.set(addr, fc->size() , 1024*SmallForLinearAlloc, fc->size()); // Note that _unallocated_block is not updated here. // Allocations from the linear allocation block should // update it. } else { _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc); } // CMSIndexedFreeListReplenish should be at least 1 CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish); _promoInfo.setSpace(this); if (UseCMSBestFit) { _fitStrategy = FreeBlockBestFitFirst; } else { _fitStrategy = FreeBlockStrategyNone; } checkFreeListConsistency(); // Initialize locks for parallel case. if (ParallelGCThreads > 0) { for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { _indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1 "a freelist par lock", true); if (_indexedFreeListParLocks[i] == NULL) vm_exit_during_initialization("Could not allocate a par lock"); DEBUG_ONLY( _indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]); ) } _dictionary->set_par_lock(&_parDictionaryAllocLock); } } // Like CompactibleSpace forward() but always calls cross_threshold() to // update the block offset table. Removed initialize_threshold call because // CFLS does not use a block offset array for contiguous spaces. HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top) { // q is alive // First check if we should switch compaction space assert(this == cp->space, "'this' should be current compaction space."); size_t compaction_max_size = pointer_delta(end(), compact_top); assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size), "virtual adjustObjectSize_v() method is not correct"); size_t adjusted_size = adjustObjectSize(size); assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0, "no small fragments allowed"); assert(minimum_free_block_size() == MinChunkSize, "for de-virtualized reference below"); // Can't leave a nonzero size, residual fragment smaller than MinChunkSize if (adjusted_size + MinChunkSize > compaction_max_size && adjusted_size != compaction_max_size) { do { // switch to next compaction space cp->space->set_compaction_top(compact_top); cp->space = cp->space->next_compaction_space(); if (cp->space == NULL) { cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen); assert(cp->gen != NULL, "compaction must succeed"); cp->space = cp->gen->first_compaction_space(); assert(cp->space != NULL, "generation must have a first compaction space"); } compact_top = cp->space->bottom(); cp->space->set_compaction_top(compact_top); // The correct adjusted_size may not be the same as that for this method // (i.e., cp->space may no longer be "this" so adjust the size again. // Use the virtual method which is not used above to save the virtual // dispatch. adjusted_size = cp->space->adjust_object_size_v(size); compaction_max_size = pointer_delta(cp->space->end(), compact_top); assert(cp->space->minimum_free_block_size() == 0, "just checking"); } while (adjusted_size > compaction_max_size); } // store the forwarding pointer into the mark word if ((HeapWord*)q != compact_top) { q->forward_to(oop(compact_top)); assert(q->is_gc_marked(), "encoding the pointer should preserve the mark"); } else { // if the object isn't moving we can just set the mark to the default // mark and handle it specially later on. q->init_mark(); assert(q->forwardee() == NULL, "should be forwarded to NULL"); } VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(q, adjusted_size)); compact_top += adjusted_size; // we need to update the offset table so that the beginnings of objects can be // found during scavenge. Note that we are updating the offset table based on // where the object will be once the compaction phase finishes. // Always call cross_threshold(). A contiguous space can only call it when // the compaction_top exceeds the current threshold but not for an // non-contiguous space. cp->threshold = cp->space->cross_threshold(compact_top - adjusted_size, compact_top); return compact_top; } // A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt // and use of single_block instead of alloc_block. The name here is not really // appropriate - maybe a more general name could be invented for both the // contiguous and noncontiguous spaces. HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) { _bt.single_block(start, the_end); return end(); } // Initialize them to NULL. void CompactibleFreeListSpace::initializeIndexedFreeListArray() { for (size_t i = 0; i < IndexSetSize; i++) { // Note that on platforms where objects are double word aligned, // the odd array elements are not used. It is convenient, however, // to map directly from the object size to the array element. _indexedFreeList[i].reset(IndexSetSize); _indexedFreeList[i].set_size(i); assert(_indexedFreeList[i].count() == 0, "reset check failed"); assert(_indexedFreeList[i].head() == NULL, "reset check failed"); assert(_indexedFreeList[i].tail() == NULL, "reset check failed"); assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed"); } } void CompactibleFreeListSpace::resetIndexedFreeListArray() { for (int i = 1; i < IndexSetSize; i++) { assert(_indexedFreeList[i].size() == (size_t) i, "Indexed free list sizes are incorrect"); _indexedFreeList[i].reset(IndexSetSize); assert(_indexedFreeList[i].count() == 0, "reset check failed"); assert(_indexedFreeList[i].head() == NULL, "reset check failed"); assert(_indexedFreeList[i].tail() == NULL, "reset check failed"); assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed"); } } void CompactibleFreeListSpace::reset(MemRegion mr) { resetIndexedFreeListArray(); dictionary()->reset(); if (BlockOffsetArrayUseUnallocatedBlock) { assert(end() == mr.end(), "We are compacting to the bottom of CMS gen"); // Everything's allocated until proven otherwise. _bt.set_unallocated_block(end()); } if (!mr.is_empty()) { assert(mr.word_size() >= MinChunkSize, "Chunk size is too small"); _bt.single_block(mr.start(), mr.word_size()); FreeChunk* fc = (FreeChunk*) mr.start(); fc->setSize(mr.word_size()); if (mr.word_size() >= IndexSetSize ) { returnChunkToDictionary(fc); } else { _bt.verify_not_unallocated((HeapWord*)fc, fc->size()); _indexedFreeList[mr.word_size()].returnChunkAtHead(fc); } } _promoInfo.reset(); _smallLinearAllocBlock._ptr = NULL; _smallLinearAllocBlock._word_size = 0; } void CompactibleFreeListSpace::reset_after_compaction() { // Reset the space to the new reality - one free chunk. MemRegion mr(compaction_top(), end()); reset(mr); // Now refill the linear allocation block(s) if possible. if (_adaptive_freelists) { refillLinearAllocBlocksIfNeeded(); } else { // Place as much of mr in the linAB as we can get, // provided it was big enough to go into the dictionary. FreeChunk* fc = dictionary()->findLargestDict(); if (fc != NULL) { assert(fc->size() == mr.word_size(), "Why was the chunk broken up?"); removeChunkFromDictionary(fc); HeapWord* addr = (HeapWord*) fc; _smallLinearAllocBlock.set(addr, fc->size() , 1024*SmallForLinearAlloc, fc->size()); // Note that _unallocated_block is not updated here. } } } // Walks the entire dictionary, returning a coterminal // chunk, if it exists. Use with caution since it involves // a potentially complete walk of a potentially large tree. FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() { assert_lock_strong(&_freelistLock); return dictionary()->find_chunk_ends_at(end()); } #ifndef PRODUCT void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() { for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { _indexedFreeList[i].allocation_stats()->set_returnedBytes(0); } } size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() { size_t sum = 0; for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { sum += _indexedFreeList[i].allocation_stats()->returnedBytes(); } return sum; } size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const { size_t count = 0; for (int i = MinChunkSize; i < IndexSetSize; i++) { debug_only( ssize_t total_list_count = 0; for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) { total_list_count++; } assert(total_list_count == _indexedFreeList[i].count(), "Count in list is incorrect"); ) count += _indexedFreeList[i].count(); } return count; } size_t CompactibleFreeListSpace::totalCount() { size_t num = totalCountInIndexedFreeLists(); num += dictionary()->totalCount(); if (_smallLinearAllocBlock._word_size != 0) { num++; } return num; } #endif bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const { FreeChunk* fc = (FreeChunk*) p; return fc->isFree(); } size_t CompactibleFreeListSpace::used() const { return capacity() - free(); } size_t CompactibleFreeListSpace::free() const { // "MT-safe, but not MT-precise"(TM), if you will: i.e. // if you do this while the structures are in flux you // may get an approximate answer only; for instance // because there is concurrent allocation either // directly by mutators or for promotion during a GC. // It's "MT-safe", however, in the sense that you are guaranteed // not to crash and burn, for instance, because of walking // pointers that could disappear as you were walking them. // The approximation is because the various components // that are read below are not read atomically (and // further the computation of totalSizeInIndexedFreeLists() // is itself a non-atomic computation. The normal use of // this is during a resize operation at the end of GC // and at that time you are guaranteed to get the // correct actual value. However, for instance, this is // also read completely asynchronously by the "perf-sampler" // that supports jvmstat, and you are apt to see the values // flicker in such cases. assert(_dictionary != NULL, "No _dictionary?"); return (_dictionary->totalChunkSize(DEBUG_ONLY(freelistLock())) + totalSizeInIndexedFreeLists() + _smallLinearAllocBlock._word_size) * HeapWordSize; } size_t CompactibleFreeListSpace::max_alloc_in_words() const { assert(_dictionary != NULL, "No _dictionary?"); assert_locked(); size_t res = _dictionary->maxChunkSize(); res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size, (size_t) SmallForLinearAlloc - 1)); // XXX the following could potentially be pretty slow; // should one, pesimally for the rare cases when res // caclulated above is less than IndexSetSize, // just return res calculated above? My reasoning was that // those cases will be so rare that the extra time spent doesn't // really matter.... // Note: do not change the loop test i >= res + IndexSetStride // to i > res below, because i is unsigned and res may be zero. for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride; i -= IndexSetStride) { if (_indexedFreeList[i].head() != NULL) { assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList"); return i; } } return res; } void CompactibleFreeListSpace::reportFreeListStatistics() const { assert_lock_strong(&_freelistLock); assert(PrintFLSStatistics != 0, "Reporting error"); _dictionary->reportStatistics(); if (PrintFLSStatistics > 1) { reportIndexedFreeListStatistics(); size_t totalSize = totalSizeInIndexedFreeLists() + _dictionary->totalChunkSize(DEBUG_ONLY(freelistLock())); gclog_or_tty->print(" free=%ld frag=%1.4f\n", totalSize, flsFrag()); } } void CompactibleFreeListSpace::reportIndexedFreeListStatistics() const { assert_lock_strong(&_freelistLock); gclog_or_tty->print("Statistics for IndexedFreeLists:\n" "--------------------------------\n"); size_t totalSize = totalSizeInIndexedFreeLists(); size_t freeBlocks = numFreeBlocksInIndexedFreeLists(); gclog_or_tty->print("Total Free Space: %d\n", totalSize); gclog_or_tty->print("Max Chunk Size: %d\n", maxChunkSizeInIndexedFreeLists()); gclog_or_tty->print("Number of Blocks: %d\n", freeBlocks); if (freeBlocks != 0) { gclog_or_tty->print("Av. Block Size: %d\n", totalSize/freeBlocks); } } size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const { size_t res = 0; for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { debug_only( ssize_t recount = 0; for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) { recount += 1; } assert(recount == _indexedFreeList[i].count(), "Incorrect count in list"); ) res += _indexedFreeList[i].count(); } return res; } size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const { for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) { if (_indexedFreeList[i].head() != NULL) { assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList"); return (size_t)i; } } return 0; } void CompactibleFreeListSpace::set_end(HeapWord* value) { HeapWord* prevEnd = end(); assert(prevEnd != value, "unnecessary set_end call"); assert(prevEnd == NULL || value >= unallocated_block(), "New end is below unallocated block"); _end = value; if (prevEnd != NULL) { // Resize the underlying block offset table. _bt.resize(pointer_delta(value, bottom())); if (value <= prevEnd) { assert(value >= unallocated_block(), "New end is below unallocated block"); } else { // Now, take this new chunk and add it to the free blocks. // Note that the BOT has not yet been updated for this block. size_t newFcSize = pointer_delta(value, prevEnd); // XXX This is REALLY UGLY and should be fixed up. XXX if (!_adaptive_freelists && _smallLinearAllocBlock._ptr == NULL) { // Mark the boundary of the new block in BOT _bt.mark_block(prevEnd, value); // put it all in the linAB if (ParallelGCThreads == 0) { _smallLinearAllocBlock._ptr = prevEnd; _smallLinearAllocBlock._word_size = newFcSize; repairLinearAllocBlock(&_smallLinearAllocBlock); } else { // ParallelGCThreads > 0 MutexLockerEx x(parDictionaryAllocLock(), Mutex::_no_safepoint_check_flag); _smallLinearAllocBlock._ptr = prevEnd; _smallLinearAllocBlock._word_size = newFcSize; repairLinearAllocBlock(&_smallLinearAllocBlock); } // Births of chunks put into a LinAB are not recorded. Births // of chunks as they are allocated out of a LinAB are. } else { // Add the block to the free lists, if possible coalescing it // with the last free block, and update the BOT and census data. addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize); } } } } class FreeListSpace_DCTOC : public Filtering_DCTOC { CompactibleFreeListSpace* _cfls; CMSCollector* _collector; protected: // Override. #define walk_mem_region_with_cl_DECL(ClosureType) \ virtual void walk_mem_region_with_cl(MemRegion mr, \ HeapWord* bottom, HeapWord* top, \ ClosureType* cl); \ void walk_mem_region_with_cl_par(MemRegion mr, \ HeapWord* bottom, HeapWord* top, \ ClosureType* cl); \ void walk_mem_region_with_cl_nopar(MemRegion mr, \ HeapWord* bottom, HeapWord* top, \ ClosureType* cl) walk_mem_region_with_cl_DECL(OopClosure); walk_mem_region_with_cl_DECL(FilteringClosure); public: FreeListSpace_DCTOC(CompactibleFreeListSpace* sp, CMSCollector* collector, OopClosure* cl, CardTableModRefBS::PrecisionStyle precision, HeapWord* boundary) : Filtering_DCTOC(sp, cl, precision, boundary), _cfls(sp), _collector(collector) {} }; // We de-virtualize the block-related calls below, since we know that our // space is a CompactibleFreeListSpace. #define FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \ void FreeListSpace_DCTOC::walk_mem_region_with_cl(MemRegion mr, \ HeapWord* bottom, \ HeapWord* top, \ ClosureType* cl) { \ if (SharedHeap::heap()->n_par_threads() > 0) { \ walk_mem_region_with_cl_par(mr, bottom, top, cl); \ } else { \ walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \ } \ } \ void FreeListSpace_DCTOC::walk_mem_region_with_cl_par(MemRegion mr, \ HeapWord* bottom, \ HeapWord* top, \ ClosureType* cl) { \ /* Skip parts that are before "mr", in case "block_start" sent us \ back too far. */ \ HeapWord* mr_start = mr.start(); \ size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \ HeapWord* next = bottom + bot_size; \ while (next < mr_start) { \ bottom = next; \ bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \ next = bottom + bot_size; \ } \ \ while (bottom < top) { \ if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \ !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \ oop(bottom)) && \ !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \ size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \ bottom += _cfls->adjustObjectSize(word_sz); \ } else { \ bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \ } \ } \ } \ void FreeListSpace_DCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \ HeapWord* bottom, \ HeapWord* top, \ ClosureType* cl) { \ /* Skip parts that are before "mr", in case "block_start" sent us \ back too far. */ \ HeapWord* mr_start = mr.start(); \ size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \ HeapWord* next = bottom + bot_size; \ while (next < mr_start) { \ bottom = next; \ bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \ next = bottom + bot_size; \ } \ \ while (bottom < top) { \ if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \ !_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \ oop(bottom)) && \ !_collector->CMSCollector::is_dead_obj(oop(bottom))) { \ size_t word_sz = oop(bottom)->oop_iterate(cl, mr); \ bottom += _cfls->adjustObjectSize(word_sz); \ } else { \ bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \ } \ } \ } // (There are only two of these, rather than N, because the split is due // only to the introduction of the FilteringClosure, a local part of the // impl of this abstraction.) FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(OopClosure) FreeListSpace_DCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure) DirtyCardToOopClosure* CompactibleFreeListSpace::new_dcto_cl(OopClosure* cl, CardTableModRefBS::PrecisionStyle precision, HeapWord* boundary) { return new FreeListSpace_DCTOC(this, _collector, cl, precision, boundary); } // Note on locking for the space iteration functions: // since the collector's iteration activities are concurrent with // allocation activities by mutators, absent a suitable mutual exclusion // mechanism the iterators may go awry. For instace a block being iterated // may suddenly be allocated or divided up and part of it allocated and // so on. // Apply the given closure to each block in the space. void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) { assert_lock_strong(freelistLock()); HeapWord *cur, *limit; for (cur = bottom(), limit = end(); cur < limit; cur += cl->do_blk_careful(cur)); } // Apply the given closure to each block in the space. void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) { assert_lock_strong(freelistLock()); HeapWord *cur, *limit; for (cur = bottom(), limit = end(); cur < limit; cur += cl->do_blk(cur)); } // Apply the given closure to each oop in the space. void CompactibleFreeListSpace::oop_iterate(OopClosure* cl) { assert_lock_strong(freelistLock()); HeapWord *cur, *limit; size_t curSize; for (cur = bottom(), limit = end(); cur < limit; cur += curSize) { curSize = block_size(cur); if (block_is_obj(cur)) { oop(cur)->oop_iterate(cl); } } } // Apply the given closure to each oop in the space \intersect memory region. void CompactibleFreeListSpace::oop_iterate(MemRegion mr, OopClosure* cl) { assert_lock_strong(freelistLock()); if (is_empty()) { return; } MemRegion cur = MemRegion(bottom(), end()); mr = mr.intersection(cur); if (mr.is_empty()) { return; } if (mr.equals(cur)) { oop_iterate(cl); return; } assert(mr.end() <= end(), "just took an intersection above"); HeapWord* obj_addr = block_start(mr.start()); HeapWord* t = mr.end(); SpaceMemRegionOopsIterClosure smr_blk(cl, mr); if (block_is_obj(obj_addr)) { // Handle first object specially. oop obj = oop(obj_addr); obj_addr += adjustObjectSize(obj->oop_iterate(&smr_blk)); } else { FreeChunk* fc = (FreeChunk*)obj_addr; obj_addr += fc->size(); } while (obj_addr < t) { HeapWord* obj = obj_addr; obj_addr += block_size(obj_addr); // If "obj_addr" is not greater than top, then the // entire object "obj" is within the region. if (obj_addr <= t) { if (block_is_obj(obj)) { oop(obj)->oop_iterate(cl); } } else { // "obj" extends beyond end of region if (block_is_obj(obj)) { oop(obj)->oop_iterate(&smr_blk); } break; } } } // NOTE: In the following methods, in order to safely be able to // apply the closure to an object, we need to be sure that the // object has been initialized. We are guaranteed that an object // is initialized if we are holding the Heap_lock with the // world stopped. void CompactibleFreeListSpace::verify_objects_initialized() const { if (is_init_completed()) { assert_locked_or_safepoint(Heap_lock); if (Universe::is_fully_initialized()) { guarantee(SafepointSynchronize::is_at_safepoint(), "Required for objects to be initialized"); } } // else make a concession at vm start-up } // Apply the given closure to each object in the space void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) { assert_lock_strong(freelistLock()); NOT_PRODUCT(verify_objects_initialized()); HeapWord *cur, *limit; size_t curSize; for (cur = bottom(), limit = end(); cur < limit; cur += curSize) { curSize = block_size(cur); if (block_is_obj(cur)) { blk->do_object(oop(cur)); } } } // Apply the given closure to each live object in the space // The usage of CompactibleFreeListSpace // by the ConcurrentMarkSweepGeneration for concurrent GC's allows // objects in the space with references to objects that are no longer // valid. For example, an object may reference another object // that has already been sweep up (collected). This method uses // obj_is_alive() to determine whether it is safe to apply the closure to // an object. See obj_is_alive() for details on how liveness of an // object is decided. void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) { assert_lock_strong(freelistLock()); NOT_PRODUCT(verify_objects_initialized()); HeapWord *cur, *limit; size_t curSize; for (cur = bottom(), limit = end(); cur < limit; cur += curSize) { curSize = block_size(cur); if (block_is_obj(cur) && obj_is_alive(cur)) { blk->do_object(oop(cur)); } } } void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl) { assert_locked(); NOT_PRODUCT(verify_objects_initialized()); Space::object_iterate_mem(mr, cl); } // Callers of this iterator beware: The closure application should // be robust in the face of uninitialized objects and should (always) // return a correct size so that the next addr + size below gives us a // valid block boundary. [See for instance, // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful() // in ConcurrentMarkSweepGeneration.cpp.] HeapWord* CompactibleFreeListSpace::object_iterate_careful(ObjectClosureCareful* cl) { assert_lock_strong(freelistLock()); HeapWord *addr, *last; size_t size; for (addr = bottom(), last = end(); addr < last; addr += size) { FreeChunk* fc = (FreeChunk*)addr; if (fc->isFree()) { // Since we hold the free list lock, which protects direct // allocation in this generation by mutators, a free object // will remain free throughout this iteration code. size = fc->size(); } else { // Note that the object need not necessarily be initialized, // because (for instance) the free list lock does NOT protect // object initialization. The closure application below must // therefore be correct in the face of uninitialized objects. size = cl->do_object_careful(oop(addr)); if (size == 0) { // An unparsable object found. Signal early termination. return addr; } } } return NULL; } // Callers of this iterator beware: The closure application should // be robust in the face of uninitialized objects and should (always) // return a correct size so that the next addr + size below gives us a // valid block boundary. [See for instance, // ScanMarkedObjectsAgainCarefullyClosure::do_object_careful() // in ConcurrentMarkSweepGeneration.cpp.] HeapWord* CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr, ObjectClosureCareful* cl) { assert_lock_strong(freelistLock()); // Can't use used_region() below because it may not necessarily // be the same as [bottom(),end()); although we could // use [used_region().start(),round_to(used_region().end(),CardSize)), // that appears too cumbersome, so we just do the simpler check // in the assertion below. assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr), "mr should be non-empty and within used space"); HeapWord *addr, *end; size_t size; for (addr = block_start_careful(mr.start()), end = mr.end(); addr < end; addr += size) { FreeChunk* fc = (FreeChunk*)addr; if (fc->isFree()) { // Since we hold the free list lock, which protects direct // allocation in this generation by mutators, a free object // will remain free throughout this iteration code. size = fc->size(); } else { // Note that the object need not necessarily be initialized, // because (for instance) the free list lock does NOT protect // object initialization. The closure application below must // therefore be correct in the face of uninitialized objects. size = cl->do_object_careful_m(oop(addr), mr); if (size == 0) { // An unparsable object found. Signal early termination. return addr; } } } return NULL; } HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const { NOT_PRODUCT(verify_objects_initialized()); return _bt.block_start(p); } HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const { return _bt.block_start_careful(p); } size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const { NOT_PRODUCT(verify_objects_initialized()); assert(MemRegion(bottom(), end()).contains(p), "p not in space"); // This must be volatile, or else there is a danger that the compiler // will compile the code below into a sometimes-infinite loop, by keeping // the value read the first time in a register. while (true) { // We must do this until we get a consistent view of the object. if (FreeChunk::indicatesFreeChunk(p)) { volatile FreeChunk* fc = (volatile FreeChunk*)p; size_t res = fc->size(); // If the object is still a free chunk, return the size, else it // has been allocated so try again. if (FreeChunk::indicatesFreeChunk(p)) { assert(res != 0, "Block size should not be 0"); return res; } } else { // must read from what 'p' points to in each loop. klassOop k = ((volatile oopDesc*)p)->klass_or_null(); if (k != NULL) { assert(k->is_oop(true /* ignore mark word */), "Should really be klass oop."); oop o = (oop)p; assert(o->is_parsable(), "Should be parsable"); assert(o->is_oop(true /* ignore mark word */), "Should be an oop."); size_t res = o->size_given_klass(k->klass_part()); res = adjustObjectSize(res); assert(res != 0, "Block size should not be 0"); return res; } } } } // A variant of the above that uses the Printezis bits for // unparsable but allocated objects. This avoids any possible // stalls waiting for mutators to initialize objects, and is // thus potentially faster than the variant above. However, // this variant may return a zero size for a block that is // under mutation and for which a consistent size cannot be // inferred without stalling; see CMSCollector::block_size_if_printezis_bits(). size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p, const CMSCollector* c) const { assert(MemRegion(bottom(), end()).contains(p), "p not in space"); // This must be volatile, or else there is a danger that the compiler // will compile the code below into a sometimes-infinite loop, by keeping // the value read the first time in a register. DEBUG_ONLY(uint loops = 0;) while (true) { // We must do this until we get a consistent view of the object. if (FreeChunk::indicatesFreeChunk(p)) { volatile FreeChunk* fc = (volatile FreeChunk*)p; size_t res = fc->size(); if (FreeChunk::indicatesFreeChunk(p)) { assert(res != 0, "Block size should not be 0"); assert(loops == 0, "Should be 0"); return res; } } else { // must read from what 'p' points to in each loop. klassOop k = ((volatile oopDesc*)p)->klass_or_null(); if (k != NULL && ((oopDesc*)p)->is_parsable() && ((oopDesc*)p)->is_conc_safe()) { assert(k->is_oop(), "Should really be klass oop."); oop o = (oop)p; assert(o->is_oop(), "Should be an oop"); size_t res = o->size_given_klass(k->klass_part()); res = adjustObjectSize(res); assert(res != 0, "Block size should not be 0"); return res; } else { return c->block_size_if_printezis_bits(p); } } assert(loops == 0, "Can loop at most once"); DEBUG_ONLY(loops++;) } } size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const { NOT_PRODUCT(verify_objects_initialized()); assert(MemRegion(bottom(), end()).contains(p), "p not in space"); FreeChunk* fc = (FreeChunk*)p; if (fc->isFree()) { return fc->size(); } else { // Ignore mark word because this may be a recently promoted // object whose mark word is used to chain together grey // objects (the last one would have a null value). assert(oop(p)->is_oop(true), "Should be an oop"); return adjustObjectSize(oop(p)->size()); } } // This implementation assumes that the property of "being an object" is // stable. But being a free chunk may not be (because of parallel // promotion.) bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const { FreeChunk* fc = (FreeChunk*)p; assert(is_in_reserved(p), "Should be in space"); // When doing a mark-sweep-compact of the CMS generation, this // assertion may fail because prepare_for_compaction() uses // space that is garbage to maintain information on ranges of // live objects so that these live ranges can be moved as a whole. // Comment out this assertion until that problem can be solved // (i.e., that the block start calculation may look at objects // at address below "p" in finding the object that contains "p" // and those objects (if garbage) may have been modified to hold // live range information. // assert(ParallelGCThreads > 0 || _bt.block_start(p) == p, "Should be a block boundary"); if (FreeChunk::indicatesFreeChunk(p)) return false; klassOop k = oop(p)->klass_or_null(); if (k != NULL) { // Ignore mark word because it may have been used to // chain together promoted objects (the last one // would have a null value). assert(oop(p)->is_oop(true), "Should be an oop"); return true; } else { return false; // Was not an object at the start of collection. } } // Check if the object is alive. This fact is checked either by consulting // the main marking bitmap in the sweeping phase or, if it's a permanent // generation and we're not in the sweeping phase, by checking the // perm_gen_verify_bit_map where we store the "deadness" information if // we did not sweep the perm gen in the most recent previous GC cycle. bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const { assert (block_is_obj(p), "The address should point to an object"); // If we're sweeping, we use object liveness information from the main bit map // for both perm gen and old gen. // We don't need to lock the bitmap (live_map or dead_map below), because // EITHER we are in the middle of the sweeping phase, and the // main marking bit map (live_map below) is locked, // OR we're in other phases and perm_gen_verify_bit_map (dead_map below) // is stable, because it's mutated only in the sweeping phase. if (_collector->abstract_state() == CMSCollector::Sweeping) { CMSBitMap* live_map = _collector->markBitMap(); return live_map->isMarked((HeapWord*) p); } else { // If we're not currently sweeping and we haven't swept the perm gen in // the previous concurrent cycle then we may have dead but unswept objects // in the perm gen. In this case, we use the "deadness" information // that we had saved in perm_gen_verify_bit_map at the last sweep. if (!CMSClassUnloadingEnabled && _collector->_permGen->reserved().contains(p)) { if (_collector->verifying()) { CMSBitMap* dead_map = _collector->perm_gen_verify_bit_map(); // Object is marked in the dead_map bitmap at the previous sweep // when we know that it's dead; if the bitmap is not allocated then // the object is alive. return (dead_map->sizeInBits() == 0) // bit_map has been allocated || !dead_map->par_isMarked((HeapWord*) p); } else { return false; // We can't say for sure if it's live, so we say that it's dead. } } } return true; } bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const { FreeChunk* fc = (FreeChunk*)p; assert(is_in_reserved(p), "Should be in space"); assert(_bt.block_start(p) == p, "Should be a block boundary"); if (!fc->isFree()) { // Ignore mark word because it may have been used to // chain together promoted objects (the last one // would have a null value). assert(oop(p)->is_oop(true), "Should be an oop"); return true; } return false; } // "MT-safe but not guaranteed MT-precise" (TM); you may get an // approximate answer if you don't hold the freelistlock when you call this. size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const { size_t size = 0; for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { debug_only( // We may be calling here without the lock in which case we // won't do this modest sanity check. if (freelistLock()->owned_by_self()) { size_t total_list_size = 0; for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) { total_list_size += i; } assert(total_list_size == i * _indexedFreeList[i].count(), "Count in list is incorrect"); } ) size += i * _indexedFreeList[i].count(); } return size; } HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) { MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag); return allocate(size); } HeapWord* CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) { return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size); } HeapWord* CompactibleFreeListSpace::allocate(size_t size) { assert_lock_strong(freelistLock()); HeapWord* res = NULL; assert(size == adjustObjectSize(size), "use adjustObjectSize() before calling into allocate()"); if (_adaptive_freelists) { res = allocate_adaptive_freelists(size); } else { // non-adaptive free lists res = allocate_non_adaptive_freelists(size); } if (res != NULL) { // check that res does lie in this space! assert(is_in_reserved(res), "Not in this space!"); assert(is_aligned((void*)res), "alignment check"); FreeChunk* fc = (FreeChunk*)res; fc->markNotFree(); assert(!fc->isFree(), "shouldn't be marked free"); assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized"); // Verify that the block offset table shows this to // be a single block, but not one which is unallocated. _bt.verify_single_block(res, size); _bt.verify_not_unallocated(res, size); // mangle a just allocated object with a distinct pattern. debug_only(fc->mangleAllocated(size)); } return res; } HeapWord* CompactibleFreeListSpace::allocate_non_adaptive_freelists(size_t size) { HeapWord* res = NULL; // try and use linear allocation for smaller blocks if (size < _smallLinearAllocBlock._allocation_size_limit) { // if successful, the following also adjusts block offset table res = getChunkFromSmallLinearAllocBlock(size); } // Else triage to indexed lists for smaller sizes if (res == NULL) { if (size < SmallForDictionary) { res = (HeapWord*) getChunkFromIndexedFreeList(size); } else { // else get it from the big dictionary; if even this doesn't // work we are out of luck. res = (HeapWord*)getChunkFromDictionaryExact(size); } } return res; } HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) { assert_lock_strong(freelistLock()); HeapWord* res = NULL; assert(size == adjustObjectSize(size), "use adjustObjectSize() before calling into allocate()"); // Strategy // if small // exact size from small object indexed list if small // small or large linear allocation block (linAB) as appropriate // take from lists of greater sized chunks // else // dictionary // small or large linear allocation block if it has the space // Try allocating exact size from indexTable first if (size < IndexSetSize) { res = (HeapWord*) getChunkFromIndexedFreeList(size); if(res != NULL) { assert(res != (HeapWord*)_indexedFreeList[size].head(), "Not removed from free list"); // no block offset table adjustment is necessary on blocks in // the indexed lists. // Try allocating from the small LinAB } else if (size < _smallLinearAllocBlock._allocation_size_limit && (res = getChunkFromSmallLinearAllocBlock(size)) != NULL) { // if successful, the above also adjusts block offset table // Note that this call will refill the LinAB to // satisfy the request. This is different that // evm. // Don't record chunk off a LinAB? smallSplitBirth(size); } else { // Raid the exact free lists larger than size, even if they are not // overpopulated. res = (HeapWord*) getChunkFromGreater(size); } } else { // Big objects get allocated directly from the dictionary. res = (HeapWord*) getChunkFromDictionaryExact(size); if (res == NULL) { // Try hard not to fail since an allocation failure will likely // trigger a synchronous GC. Try to get the space from the // allocation blocks. res = getChunkFromSmallLinearAllocBlockRemainder(size); } } return res; } // A worst-case estimate of the space required (in HeapWords) to expand the heap // when promoting obj. size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const { // Depending on the object size, expansion may require refilling either a // bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize // is added because the dictionary may over-allocate to avoid fragmentation. size_t space = obj_size; if (!_adaptive_freelists) { space = MAX2(space, _smallLinearAllocBlock._refillSize); } space += _promoInfo.refillSize() + 2 * MinChunkSize; return space; } FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) { FreeChunk* ret; assert(numWords >= MinChunkSize, "Size is less than minimum"); assert(linearAllocationWouldFail() || bestFitFirst(), "Should not be here"); size_t i; size_t currSize = numWords + MinChunkSize; assert(currSize % MinObjAlignment == 0, "currSize should be aligned"); for (i = currSize; i < IndexSetSize; i += IndexSetStride) { FreeList* fl = &_indexedFreeList[i]; if (fl->head()) { ret = getFromListGreater(fl, numWords); assert(ret == NULL || ret->isFree(), "Should be returning a free chunk"); return ret; } } currSize = MAX2((size_t)SmallForDictionary, (size_t)(numWords + MinChunkSize)); /* Try to get a chunk that satisfies request, while avoiding fragmentation that can't be handled. */ { ret = dictionary()->getChunk(currSize); if (ret != NULL) { assert(ret->size() - numWords >= MinChunkSize, "Chunk is too small"); _bt.allocated((HeapWord*)ret, ret->size()); /* Carve returned chunk. */ (void) splitChunkAndReturnRemainder(ret, numWords); /* Label this as no longer a free chunk. */ assert(ret->isFree(), "This chunk should be free"); ret->linkPrev(NULL); } assert(ret == NULL || ret->isFree(), "Should be returning a free chunk"); return ret; } ShouldNotReachHere(); } bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const { assert(fc->size() < IndexSetSize, "Size of chunk is too large"); return _indexedFreeList[fc->size()].verifyChunkInFreeLists(fc); } bool CompactibleFreeListSpace::verifyChunkInFreeLists(FreeChunk* fc) const { if (fc->size() >= IndexSetSize) { return dictionary()->verifyChunkInFreeLists(fc); } else { return verifyChunkInIndexedFreeLists(fc); } } #ifndef PRODUCT void CompactibleFreeListSpace::assert_locked() const { CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock()); } #endif FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) { // In the parallel case, the main thread holds the free list lock // on behalf the parallel threads. assert_locked(); FreeChunk* fc; { // If GC is parallel, this might be called by several threads. // This should be rare enough that the locking overhead won't affect // the sequential code. MutexLockerEx x(parDictionaryAllocLock(), Mutex::_no_safepoint_check_flag); fc = getChunkFromDictionary(size); } if (fc != NULL) { fc->dontCoalesce(); assert(fc->isFree(), "Should be free, but not coalescable"); // Verify that the block offset table shows this to // be a single block, but not one which is unallocated. _bt.verify_single_block((HeapWord*)fc, fc->size()); _bt.verify_not_unallocated((HeapWord*)fc, fc->size()); } return fc; } oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) { assert(obj_size == (size_t)obj->size(), "bad obj_size passed in"); assert_locked(); // if we are tracking promotions, then first ensure space for // promotion (including spooling space for saving header if necessary). // then allocate and copy, then track promoted info if needed. // When tracking (see PromotionInfo::track()), the mark word may // be displaced and in this case restoration of the mark word // occurs in the (oop_since_save_marks_)iterate phase. if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) { return NULL; } // Call the allocate(size_t, bool) form directly to avoid the // additional call through the allocate(size_t) form. Having // the compile inline the call is problematic because allocate(size_t) // is a virtual method. HeapWord* res = allocate(adjustObjectSize(obj_size)); if (res != NULL) { Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size); // if we should be tracking promotions, do so. if (_promoInfo.tracking()) { _promoInfo.track((PromotedObject*)res); } } return oop(res); } HeapWord* CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) { assert_locked(); assert(size >= MinChunkSize, "minimum chunk size"); assert(size < _smallLinearAllocBlock._allocation_size_limit, "maximum from smallLinearAllocBlock"); return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size); } HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk, size_t size) { assert_locked(); assert(size >= MinChunkSize, "too small"); HeapWord* res = NULL; // Try to do linear allocation from blk, making sure that if (blk->_word_size == 0) { // We have probably been unable to fill this either in the prologue or // when it was exhausted at the last linear allocation. Bail out until // next time. assert(blk->_ptr == NULL, "consistency check"); return NULL; } assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check"); res = getChunkFromLinearAllocBlockRemainder(blk, size); if (res != NULL) return res; // about to exhaust this linear allocation block if (blk->_word_size == size) { // exactly satisfied res = blk->_ptr; _bt.allocated(res, blk->_word_size); } else if (size + MinChunkSize <= blk->_refillSize) { // Update _unallocated_block if the size is such that chunk would be // returned to the indexed free list. All other chunks in the indexed // free lists are allocated from the dictionary so that _unallocated_block // has already been adjusted for them. Do it here so that the cost // for all chunks added back to the indexed free lists. if (blk->_word_size < SmallForDictionary) { _bt.allocated(blk->_ptr, blk->_word_size); } // Return the chunk that isn't big enough, and then refill below. addChunkToFreeLists(blk->_ptr, blk->_word_size); _bt.verify_single_block(blk->_ptr, (blk->_ptr + blk->_word_size)); // Don't keep statistics on adding back chunk from a LinAB. } else { // A refilled block would not satisfy the request. return NULL; } blk->_ptr = NULL; blk->_word_size = 0; refillLinearAllocBlock(blk); assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize, "block was replenished"); if (res != NULL) { splitBirth(size); repairLinearAllocBlock(blk); } else if (blk->_ptr != NULL) { res = blk->_ptr; size_t blk_size = blk->_word_size; blk->_word_size -= size; blk->_ptr += size; splitBirth(size); repairLinearAllocBlock(blk); // Update BOT last so that other (parallel) GC threads see a consistent // view of the BOT and free blocks. // Above must occur before BOT is updated below. _bt.split_block(res, blk_size, size); // adjust block offset table } return res; } HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder( LinearAllocBlock* blk, size_t size) { assert_locked(); assert(size >= MinChunkSize, "too small"); HeapWord* res = NULL; // This is the common case. Keep it simple. if (blk->_word_size >= size + MinChunkSize) { assert(blk->_ptr != NULL, "consistency check"); res = blk->_ptr; // Note that the BOT is up-to-date for the linAB before allocation. It // indicates the start of the linAB. The split_block() updates the // BOT for the linAB after the allocation (indicates the start of the // next chunk to be allocated). size_t blk_size = blk->_word_size; blk->_word_size -= size; blk->_ptr += size; splitBirth(size); repairLinearAllocBlock(blk); // Update BOT last so that other (parallel) GC threads see a consistent // view of the BOT and free blocks. // Above must occur before BOT is updated below. _bt.split_block(res, blk_size, size); // adjust block offset table _bt.allocated(res, size); } return res; } FreeChunk* CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) { assert_locked(); assert(size < SmallForDictionary, "just checking"); FreeChunk* res; res = _indexedFreeList[size].getChunkAtHead(); if (res == NULL) { res = getChunkFromIndexedFreeListHelper(size); } _bt.verify_not_unallocated((HeapWord*) res, size); return res; } FreeChunk* CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size) { assert_locked(); FreeChunk* fc = NULL; if (size < SmallForDictionary) { assert(_indexedFreeList[size].head() == NULL || _indexedFreeList[size].surplus() <= 0, "List for this size should be empty or under populated"); // Try best fit in exact lists before replenishing the list if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) { // Replenish list. // // Things tried that failed. // Tried allocating out of the two LinAB's first before // replenishing lists. // Tried small linAB of size 256 (size in indexed list) // and replenishing indexed lists from the small linAB. // FreeChunk* newFc = NULL; size_t replenish_size = CMSIndexedFreeListReplenish * size; if (replenish_size < SmallForDictionary) { // Do not replenish from an underpopulated size. if (_indexedFreeList[replenish_size].surplus() > 0 && _indexedFreeList[replenish_size].head() != NULL) { newFc = _indexedFreeList[replenish_size].getChunkAtHead(); } else { newFc = bestFitSmall(replenish_size); } } if (newFc != NULL) { splitDeath(replenish_size); } else if (replenish_size > size) { assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant"); newFc = getChunkFromIndexedFreeListHelper(replenish_size); } if (newFc != NULL) { assert(newFc->size() == replenish_size, "Got wrong size"); size_t i; FreeChunk *curFc, *nextFc; // carve up and link blocks 0, ..., CMSIndexedFreeListReplenish - 2 // The last chunk is not added to the lists but is returned as the // free chunk. for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size), i = 0; i < (CMSIndexedFreeListReplenish - 1); curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size), i++) { curFc->setSize(size); // Don't record this as a return in order to try and // determine the "returns" from a GC. _bt.verify_not_unallocated((HeapWord*) fc, size); _indexedFreeList[size].returnChunkAtTail(curFc, false); _bt.mark_block((HeapWord*)curFc, size); splitBirth(size); // Don't record the initial population of the indexed list // as a split birth. } // check that the arithmetic was OK above assert((HeapWord*)nextFc == (HeapWord*)newFc + replenish_size, "inconsistency in carving newFc"); curFc->setSize(size); _bt.mark_block((HeapWord*)curFc, size); splitBirth(size); return curFc; } } } else { // Get a free chunk from the free chunk dictionary to be returned to // replenish the indexed free list. fc = getChunkFromDictionaryExact(size); } assert(fc == NULL || fc->isFree(), "Should be returning a free chunk"); return fc; } FreeChunk* CompactibleFreeListSpace::getChunkFromDictionary(size_t size) { assert_locked(); FreeChunk* fc = _dictionary->getChunk(size); if (fc == NULL) { return NULL; } _bt.allocated((HeapWord*)fc, fc->size()); if (fc->size() >= size + MinChunkSize) { fc = splitChunkAndReturnRemainder(fc, size); } assert(fc->size() >= size, "chunk too small"); assert(fc->size() < size + MinChunkSize, "chunk too big"); _bt.verify_single_block((HeapWord*)fc, fc->size()); return fc; } FreeChunk* CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) { assert_locked(); FreeChunk* fc = _dictionary->getChunk(size); if (fc == NULL) { return fc; } _bt.allocated((HeapWord*)fc, fc->size()); if (fc->size() == size) { _bt.verify_single_block((HeapWord*)fc, size); return fc; } assert(fc->size() > size, "getChunk() guarantee"); if (fc->size() < size + MinChunkSize) { // Return the chunk to the dictionary and go get a bigger one. returnChunkToDictionary(fc); fc = _dictionary->getChunk(size + MinChunkSize); if (fc == NULL) { return NULL; } _bt.allocated((HeapWord*)fc, fc->size()); } assert(fc->size() >= size + MinChunkSize, "tautology"); fc = splitChunkAndReturnRemainder(fc, size); assert(fc->size() == size, "chunk is wrong size"); _bt.verify_single_block((HeapWord*)fc, size); return fc; } void CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) { assert_locked(); size_t size = chunk->size(); _bt.verify_single_block((HeapWord*)chunk, size); // adjust _unallocated_block downward, as necessary _bt.freed((HeapWord*)chunk, size); _dictionary->returnChunk(chunk); } void CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) { assert_locked(); size_t size = fc->size(); _bt.verify_single_block((HeapWord*) fc, size); _bt.verify_not_unallocated((HeapWord*) fc, size); if (_adaptive_freelists) { _indexedFreeList[size].returnChunkAtTail(fc); } else { _indexedFreeList[size].returnChunkAtHead(fc); } } // Add chunk to end of last block -- if it's the largest // block -- and update BOT and census data. We would // of course have preferred to coalesce it with the // last block, but it's currently less expensive to find the // largest block than it is to find the last. void CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats( HeapWord* chunk, size_t size) { // check that the chunk does lie in this space! assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!"); assert_locked(); // One of the parallel gc task threads may be here // whilst others are allocating. Mutex* lock = NULL; if (ParallelGCThreads != 0) { lock = &_parDictionaryAllocLock; } FreeChunk* ec; { MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); ec = dictionary()->findLargestDict(); // get largest block if (ec != NULL && ec->end() == chunk) { // It's a coterminal block - we can coalesce. size_t old_size = ec->size(); coalDeath(old_size); removeChunkFromDictionary(ec); size += old_size; } else { ec = (FreeChunk*)chunk; } } ec->setSize(size); debug_only(ec->mangleFreed(size)); if (size < SmallForDictionary) { lock = _indexedFreeListParLocks[size]; } MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); addChunkAndRepairOffsetTable((HeapWord*)ec, size, true); // record the birth under the lock since the recording involves // manipulation of the list on which the chunk lives and // if the chunk is allocated and is the last on the list, // the list can go away. coalBirth(size); } void CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk, size_t size) { // check that the chunk does lie in this space! assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!"); assert_locked(); _bt.verify_single_block(chunk, size); FreeChunk* fc = (FreeChunk*) chunk; fc->setSize(size); debug_only(fc->mangleFreed(size)); if (size < SmallForDictionary) { returnChunkToFreeList(fc); } else { returnChunkToDictionary(fc); } } void CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size, bool coalesced) { assert_locked(); assert(chunk != NULL, "null chunk"); if (coalesced) { // repair BOT _bt.single_block(chunk, size); } addChunkToFreeLists(chunk, size); } // We _must_ find the purported chunk on our free lists; // we assert if we don't. void CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) { size_t size = fc->size(); assert_locked(); debug_only(verifyFreeLists()); if (size < SmallForDictionary) { removeChunkFromIndexedFreeList(fc); } else { removeChunkFromDictionary(fc); } _bt.verify_single_block((HeapWord*)fc, size); debug_only(verifyFreeLists()); } void CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) { size_t size = fc->size(); assert_locked(); assert(fc != NULL, "null chunk"); _bt.verify_single_block((HeapWord*)fc, size); _dictionary->removeChunk(fc); // adjust _unallocated_block upward, as necessary _bt.allocated((HeapWord*)fc, size); } void CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) { assert_locked(); size_t size = fc->size(); _bt.verify_single_block((HeapWord*)fc, size); NOT_PRODUCT( if (FLSVerifyIndexTable) { verifyIndexedFreeList(size); } ) _indexedFreeList[size].removeChunk(fc); debug_only(fc->clearNext()); debug_only(fc->clearPrev()); NOT_PRODUCT( if (FLSVerifyIndexTable) { verifyIndexedFreeList(size); } ) } FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) { /* A hint is the next larger size that has a surplus. Start search at a size large enough to guarantee that the excess is >= MIN_CHUNK. */ size_t start = align_object_size(numWords + MinChunkSize); if (start < IndexSetSize) { FreeList* it = _indexedFreeList; size_t hint = _indexedFreeList[start].hint(); while (hint < IndexSetSize) { assert(hint % MinObjAlignment == 0, "hint should be aligned"); FreeList *fl = &_indexedFreeList[hint]; if (fl->surplus() > 0 && fl->head() != NULL) { // Found a list with surplus, reset original hint // and split out a free chunk which is returned. _indexedFreeList[start].set_hint(hint); FreeChunk* res = getFromListGreater(fl, numWords); assert(res == NULL || res->isFree(), "Should be returning a free chunk"); return res; } hint = fl->hint(); /* keep looking */ } /* None found. */ it[start].set_hint(IndexSetSize); } return NULL; } /* Requires fl->size >= numWords + MinChunkSize */ FreeChunk* CompactibleFreeListSpace::getFromListGreater(FreeList* fl, size_t numWords) { FreeChunk *curr = fl->head(); size_t oldNumWords = curr->size(); assert(numWords >= MinChunkSize, "Word size is too small"); assert(curr != NULL, "List is empty"); assert(oldNumWords >= numWords + MinChunkSize, "Size of chunks in the list is too small"); fl->removeChunk(curr); // recorded indirectly by splitChunkAndReturnRemainder - // smallSplit(oldNumWords, numWords); FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords); // Does anything have to be done for the remainder in terms of // fixing the card table? assert(new_chunk == NULL || new_chunk->isFree(), "Should be returning a free chunk"); return new_chunk; } FreeChunk* CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size) { assert_locked(); size_t size = chunk->size(); assert(size > new_size, "Split from a smaller block?"); assert(is_aligned(chunk), "alignment problem"); assert(size == adjustObjectSize(size), "alignment problem"); size_t rem_size = size - new_size; assert(rem_size == adjustObjectSize(rem_size), "alignment problem"); assert(rem_size >= MinChunkSize, "Free chunk smaller than minimum"); FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size); assert(is_aligned(ffc), "alignment problem"); ffc->setSize(rem_size); ffc->linkNext(NULL); ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads. // Above must occur before BOT is updated below. // adjust block offset table _bt.split_block((HeapWord*)chunk, chunk->size(), new_size); if (rem_size < SmallForDictionary) { bool is_par = (SharedHeap::heap()->n_par_threads() > 0); if (is_par) _indexedFreeListParLocks[rem_size]->lock(); returnChunkToFreeList(ffc); split(size, rem_size); if (is_par) _indexedFreeListParLocks[rem_size]->unlock(); } else { returnChunkToDictionary(ffc); split(size ,rem_size); } chunk->setSize(new_size); return chunk; } void CompactibleFreeListSpace::sweep_completed() { // Now that space is probably plentiful, refill linear // allocation blocks as needed. refillLinearAllocBlocksIfNeeded(); } void CompactibleFreeListSpace::gc_prologue() { assert_locked(); if (PrintFLSStatistics != 0) { gclog_or_tty->print("Before GC:\n"); reportFreeListStatistics(); } refillLinearAllocBlocksIfNeeded(); } void CompactibleFreeListSpace::gc_epilogue() { assert_locked(); if (PrintGCDetails && Verbose && !_adaptive_freelists) { if (_smallLinearAllocBlock._word_size == 0) warning("CompactibleFreeListSpace(epilogue):: Linear allocation failure"); } assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); _promoInfo.stopTrackingPromotions(); repairLinearAllocationBlocks(); // Print Space's stats if (PrintFLSStatistics != 0) { gclog_or_tty->print("After GC:\n"); reportFreeListStatistics(); } } // Iteration support, mostly delegated from a CMS generation void CompactibleFreeListSpace::save_marks() { // mark the "end" of the used space at the time of this call; // note, however, that promoted objects from this point // on are tracked in the _promoInfo below. set_saved_mark_word(BlockOffsetArrayUseUnallocatedBlock ? unallocated_block() : end()); // inform allocator that promotions should be tracked. assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); _promoInfo.startTrackingPromotions(); } bool CompactibleFreeListSpace::no_allocs_since_save_marks() { assert(_promoInfo.tracking(), "No preceding save_marks?"); guarantee(SharedHeap::heap()->n_par_threads() == 0, "Shouldn't be called (yet) during parallel part of gc."); return _promoInfo.noPromotions(); } #define CFLS_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ \ void CompactibleFreeListSpace:: \ oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) { \ assert(SharedHeap::heap()->n_par_threads() == 0, \ "Shouldn't be called (yet) during parallel part of gc."); \ _promoInfo.promoted_oops_iterate##nv_suffix(blk); \ /* \ * This also restores any displaced headers and removes the elements from \ * the iteration set as they are processed, so that we have a clean slate \ * at the end of the iteration. Note, thus, that if new objects are \ * promoted as a result of the iteration they are iterated over as well. \ */ \ assert(_promoInfo.noPromotions(), "_promoInfo inconsistency"); \ } ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DEFN) ////////////////////////////////////////////////////////////////////////////// // We go over the list of promoted objects, removing each from the list, // and applying the closure (this may, in turn, add more elements to // the tail of the promoted list, and these newly added objects will // also be processed) until the list is empty. // To aid verification and debugging, in the non-product builds // we actually forward _promoHead each time we process a promoted oop. // Note that this is not necessary in general (i.e. when we don't need to // call PromotionInfo::verify()) because oop_iterate can only add to the // end of _promoTail, and never needs to look at _promoHead. #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \ \ void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \ NOT_PRODUCT(verify()); \ PromotedObject *curObj, *nextObj; \ for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \ if ((nextObj = curObj->next()) == NULL) { \ /* protect ourselves against additions due to closure application \ below by resetting the list. */ \ assert(_promoTail == curObj, "Should have been the tail"); \ _promoHead = _promoTail = NULL; \ } \ if (curObj->hasDisplacedMark()) { \ /* restore displaced header */ \ oop(curObj)->set_mark(nextDisplacedHeader()); \ } else { \ /* restore prototypical header */ \ oop(curObj)->init_mark(); \ } \ /* The "promoted_mark" should now not be set */ \ assert(!curObj->hasPromotedMark(), \ "Should have been cleared by restoring displaced mark-word"); \ NOT_PRODUCT(_promoHead = nextObj); \ if (cl != NULL) oop(curObj)->oop_iterate(cl); \ if (nextObj == NULL) { /* start at head of list reset above */ \ nextObj = _promoHead; \ } \ } \ assert(noPromotions(), "post-condition violation"); \ assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\ assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \ assert(_firstIndex == _nextIndex, "empty buffer"); \ } // This should have been ALL_SINCE_...() just like the others, // but, because the body of the method above is somehwat longer, // the MSVC compiler cannot cope; as a workaround, we split the // macro into its 3 constituent parts below (see original macro // definition in specializedOopClosures.hpp). SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN) PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v) void CompactibleFreeListSpace::object_iterate_since_last_GC(ObjectClosure* cl) { // ugghh... how would one do this efficiently for a non-contiguous space? guarantee(false, "NYI"); } bool CompactibleFreeListSpace::linearAllocationWouldFail() const { return _smallLinearAllocBlock._word_size == 0; } void CompactibleFreeListSpace::repairLinearAllocationBlocks() { // Fix up linear allocation blocks to look like free blocks repairLinearAllocBlock(&_smallLinearAllocBlock); } void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) { assert_locked(); if (blk->_ptr != NULL) { assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize, "Minimum block size requirement"); FreeChunk* fc = (FreeChunk*)(blk->_ptr); fc->setSize(blk->_word_size); fc->linkPrev(NULL); // mark as free fc->dontCoalesce(); assert(fc->isFree(), "just marked it free"); assert(fc->cantCoalesce(), "just marked it uncoalescable"); } } void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() { assert_locked(); if (_smallLinearAllocBlock._ptr == NULL) { assert(_smallLinearAllocBlock._word_size == 0, "Size of linAB should be zero if the ptr is NULL"); // Reset the linAB refill and allocation size limit. _smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc); } refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock); } void CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) { assert_locked(); assert((blk->_ptr == NULL && blk->_word_size == 0) || (blk->_ptr != NULL && blk->_word_size >= MinChunkSize), "blk invariant"); if (blk->_ptr == NULL) { refillLinearAllocBlock(blk); } if (PrintMiscellaneous && Verbose) { if (blk->_word_size == 0) { warning("CompactibleFreeListSpace(prologue):: Linear allocation failure"); } } } void CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) { assert_locked(); assert(blk->_word_size == 0 && blk->_ptr == NULL, "linear allocation block should be empty"); FreeChunk* fc; if (blk->_refillSize < SmallForDictionary && (fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) { // A linAB's strategy might be to use small sizes to reduce // fragmentation but still get the benefits of allocation from a // linAB. } else { fc = getChunkFromDictionary(blk->_refillSize); } if (fc != NULL) { blk->_ptr = (HeapWord*)fc; blk->_word_size = fc->size(); fc->dontCoalesce(); // to prevent sweeper from sweeping us up } } // Support for concurrent collection policy decisions. bool CompactibleFreeListSpace::should_concurrent_collect() const { // In the future we might want to add in frgamentation stats -- // including erosion of the "mountain" into this decision as well. return !adaptive_freelists() && linearAllocationWouldFail(); } // Support for compaction void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) { SCAN_AND_FORWARD(cp,end,block_is_obj,block_size); // prepare_for_compaction() uses the space between live objects // so that later phase can skip dead space quickly. So verification // of the free lists doesn't work after. } #define obj_size(q) adjustObjectSize(oop(q)->size()) #define adjust_obj_size(s) adjustObjectSize(s) void CompactibleFreeListSpace::adjust_pointers() { // In other versions of adjust_pointers(), a bail out // based on the amount of live data in the generation // (i.e., if 0, bail out) may be used. // Cannot test used() == 0 here because the free lists have already // been mangled by the compaction. SCAN_AND_ADJUST_POINTERS(adjust_obj_size); // See note about verification in prepare_for_compaction(). } void CompactibleFreeListSpace::compact() { SCAN_AND_COMPACT(obj_size); } // fragmentation_metric = 1 - [sum of (fbs**2) / (sum of fbs)**2] // where fbs is free block sizes double CompactibleFreeListSpace::flsFrag() const { size_t itabFree = totalSizeInIndexedFreeLists(); double frag = 0.0; size_t i; for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { double sz = i; frag += _indexedFreeList[i].count() * (sz * sz); } double totFree = itabFree + _dictionary->totalChunkSize(DEBUG_ONLY(freelistLock())); if (totFree > 0) { frag = ((frag + _dictionary->sum_of_squared_block_sizes()) / (totFree * totFree)); frag = (double)1.0 - frag; } else { assert(frag == 0.0, "Follows from totFree == 0"); } return frag; } #define CoalSurplusPercent 1.05 #define SplitSurplusPercent 1.10 void CompactibleFreeListSpace::beginSweepFLCensus( float inter_sweep_current, float inter_sweep_estimate) { assert_locked(); size_t i; for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { FreeList* fl = &_indexedFreeList[i]; fl->compute_desired(inter_sweep_current, inter_sweep_estimate); fl->set_coalDesired((ssize_t)((double)fl->desired() * CoalSurplusPercent)); fl->set_beforeSweep(fl->count()); fl->set_bfrSurp(fl->surplus()); } _dictionary->beginSweepDictCensus(CoalSurplusPercent, inter_sweep_current, inter_sweep_estimate); } void CompactibleFreeListSpace::setFLSurplus() { assert_locked(); size_t i; for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { FreeList *fl = &_indexedFreeList[i]; fl->set_surplus(fl->count() - (ssize_t)((double)fl->desired() * SplitSurplusPercent)); } } void CompactibleFreeListSpace::setFLHints() { assert_locked(); size_t i; size_t h = IndexSetSize; for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) { FreeList *fl = &_indexedFreeList[i]; fl->set_hint(h); if (fl->surplus() > 0) { h = i; } } } void CompactibleFreeListSpace::clearFLCensus() { assert_locked(); int i; for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { FreeList *fl = &_indexedFreeList[i]; fl->set_prevSweep(fl->count()); fl->set_coalBirths(0); fl->set_coalDeaths(0); fl->set_splitBirths(0); fl->set_splitDeaths(0); } } void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) { setFLSurplus(); setFLHints(); if (PrintGC && PrintFLSCensus > 0) { printFLCensus(sweep_count); } clearFLCensus(); assert_locked(); _dictionary->endSweepDictCensus(SplitSurplusPercent); } bool CompactibleFreeListSpace::coalOverPopulated(size_t size) { if (size < SmallForDictionary) { FreeList *fl = &_indexedFreeList[size]; return (fl->coalDesired() < 0) || ((int)fl->count() > fl->coalDesired()); } else { return dictionary()->coalDictOverPopulated(size); } } void CompactibleFreeListSpace::smallCoalBirth(size_t size) { assert(size < SmallForDictionary, "Size too large for indexed list"); FreeList *fl = &_indexedFreeList[size]; fl->increment_coalBirths(); fl->increment_surplus(); } void CompactibleFreeListSpace::smallCoalDeath(size_t size) { assert(size < SmallForDictionary, "Size too large for indexed list"); FreeList *fl = &_indexedFreeList[size]; fl->increment_coalDeaths(); fl->decrement_surplus(); } void CompactibleFreeListSpace::coalBirth(size_t size) { if (size < SmallForDictionary) { smallCoalBirth(size); } else { dictionary()->dictCensusUpdate(size, false /* split */, true /* birth */); } } void CompactibleFreeListSpace::coalDeath(size_t size) { if(size < SmallForDictionary) { smallCoalDeath(size); } else { dictionary()->dictCensusUpdate(size, false /* split */, false /* birth */); } } void CompactibleFreeListSpace::smallSplitBirth(size_t size) { assert(size < SmallForDictionary, "Size too large for indexed list"); FreeList *fl = &_indexedFreeList[size]; fl->increment_splitBirths(); fl->increment_surplus(); } void CompactibleFreeListSpace::smallSplitDeath(size_t size) { assert(size < SmallForDictionary, "Size too large for indexed list"); FreeList *fl = &_indexedFreeList[size]; fl->increment_splitDeaths(); fl->decrement_surplus(); } void CompactibleFreeListSpace::splitBirth(size_t size) { if (size < SmallForDictionary) { smallSplitBirth(size); } else { dictionary()->dictCensusUpdate(size, true /* split */, true /* birth */); } } void CompactibleFreeListSpace::splitDeath(size_t size) { if (size < SmallForDictionary) { smallSplitDeath(size); } else { dictionary()->dictCensusUpdate(size, true /* split */, false /* birth */); } } void CompactibleFreeListSpace::split(size_t from, size_t to1) { size_t to2 = from - to1; splitDeath(from); splitBirth(to1); splitBirth(to2); } void CompactibleFreeListSpace::print() const { tty->print(" CompactibleFreeListSpace"); Space::print(); } void CompactibleFreeListSpace::prepare_for_verify() { assert_locked(); repairLinearAllocationBlocks(); // Verify that the SpoolBlocks look like free blocks of // appropriate sizes... To be done ... } class VerifyAllBlksClosure: public BlkClosure { private: const CompactibleFreeListSpace* _sp; const MemRegion _span; public: VerifyAllBlksClosure(const CompactibleFreeListSpace* sp, MemRegion span) : _sp(sp), _span(span) { } virtual size_t do_blk(HeapWord* addr) { size_t res; if (_sp->block_is_obj(addr)) { oop p = oop(addr); guarantee(p->is_oop(), "Should be an oop"); res = _sp->adjustObjectSize(p->size()); if (_sp->obj_is_alive(addr)) { p->verify(); } } else { FreeChunk* fc = (FreeChunk*)addr; res = fc->size(); if (FLSVerifyLists && !fc->cantCoalesce()) { guarantee(_sp->verifyChunkInFreeLists(fc), "Chunk should be on a free list"); } } guarantee(res != 0, "Livelock: no rank reduction!"); return res; } }; class VerifyAllOopsClosure: public OopClosure { private: const CMSCollector* _collector; const CompactibleFreeListSpace* _sp; const MemRegion _span; const bool _past_remark; const CMSBitMap* _bit_map; protected: void do_oop(void* p, oop obj) { if (_span.contains(obj)) { // the interior oop points into CMS heap if (!_span.contains(p)) { // reference from outside CMS heap // Should be a valid object; the first disjunct below allows // us to sidestep an assertion in block_is_obj() that insists // that p be in _sp. Note that several generations (and spaces) // are spanned by _span (CMS heap) above. guarantee(!_sp->is_in_reserved(obj) || _sp->block_is_obj((HeapWord*)obj), "Should be an object"); guarantee(obj->is_oop(), "Should be an oop"); obj->verify(); if (_past_remark) { // Remark has been completed, the object should be marked _bit_map->isMarked((HeapWord*)obj); } } else { // reference within CMS heap if (_past_remark) { // Remark has been completed -- so the referent should have // been marked, if referring object is. if (_bit_map->isMarked(_collector->block_start(p))) { guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?"); } } } } else if (_sp->is_in_reserved(p)) { // the reference is from FLS, and points out of FLS guarantee(obj->is_oop(), "Should be an oop"); obj->verify(); } } template <class T> void do_oop_work(T* p) { T heap_oop = oopDesc::load_heap_oop(p); if (!oopDesc::is_null(heap_oop)) { oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); do_oop(p, obj); } } public: VerifyAllOopsClosure(const CMSCollector* collector, const CompactibleFreeListSpace* sp, MemRegion span, bool past_remark, CMSBitMap* bit_map) : OopClosure(), _collector(collector), _sp(sp), _span(span), _past_remark(past_remark), _bit_map(bit_map) { } virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); } virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); } }; void CompactibleFreeListSpace::verify(bool ignored) const { assert_lock_strong(&_freelistLock); verify_objects_initialized(); MemRegion span = _collector->_span; bool past_remark = (_collector->abstract_state() == CMSCollector::Sweeping); ResourceMark rm; HandleMark hm; // Check integrity of CFL data structures _promoInfo.verify(); _dictionary->verify(); if (FLSVerifyIndexTable) { verifyIndexedFreeLists(); } // Check integrity of all objects and free blocks in space { VerifyAllBlksClosure cl(this, span); ((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const } // Check that all references in the heap to FLS // are to valid objects in FLS or that references in // FLS are to valid objects elsewhere in the heap if (FLSVerifyAllHeapReferences) { VerifyAllOopsClosure cl(_collector, this, span, past_remark, _collector->markBitMap()); CollectedHeap* ch = Universe::heap(); ch->oop_iterate(&cl); // all oops in generations ch->permanent_oop_iterate(&cl); // all oops in perm gen } if (VerifyObjectStartArray) { // Verify the block offset table _bt.verify(); } } #ifndef PRODUCT void CompactibleFreeListSpace::verifyFreeLists() const { if (FLSVerifyLists) { _dictionary->verify(); verifyIndexedFreeLists(); } else { if (FLSVerifyDictionary) { _dictionary->verify(); } if (FLSVerifyIndexTable) { verifyIndexedFreeLists(); } } } #endif void CompactibleFreeListSpace::verifyIndexedFreeLists() const { size_t i = 0; for (; i < MinChunkSize; i++) { guarantee(_indexedFreeList[i].head() == NULL, "should be NULL"); } for (; i < IndexSetSize; i++) { verifyIndexedFreeList(i); } } void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const { FreeChunk* fc = _indexedFreeList[size].head(); guarantee((size % 2 == 0) || fc == NULL, "Odd slots should be empty"); for (; fc != NULL; fc = fc->next()) { guarantee(fc->size() == size, "Size inconsistency"); guarantee(fc->isFree(), "!free?"); guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list"); } } #ifndef PRODUCT void CompactibleFreeListSpace::checkFreeListConsistency() const { assert(_dictionary->minSize() <= IndexSetSize, "Some sizes can't be allocated without recourse to" " linear allocation buffers"); assert(MIN_TREE_CHUNK_SIZE*HeapWordSize == sizeof(TreeChunk), "else MIN_TREE_CHUNK_SIZE is wrong"); assert((IndexSetStride == 2 && IndexSetStart == 2) || (IndexSetStride == 1 && IndexSetStart == 1), "just checking"); assert((IndexSetStride != 2) || (MinChunkSize % 2 == 0), "Some for-loops may be incorrectly initialized"); assert((IndexSetStride != 2) || (IndexSetSize % 2 == 1), "For-loops that iterate over IndexSet with stride 2 may be wrong"); } #endif void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const { assert_lock_strong(&_freelistLock); FreeList total; gclog_or_tty->print("end sweep# " SIZE_FORMAT "\n", sweep_count); FreeList::print_labels_on(gclog_or_tty, "size"); size_t totalFree = 0; for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) { const FreeList *fl = &_indexedFreeList[i]; totalFree += fl->count() * fl->size(); if (i % (40*IndexSetStride) == 0) { FreeList::print_labels_on(gclog_or_tty, "size"); } fl->print_on(gclog_or_tty); total.set_bfrSurp( total.bfrSurp() + fl->bfrSurp() ); total.set_surplus( total.surplus() + fl->surplus() ); total.set_desired( total.desired() + fl->desired() ); total.set_prevSweep( total.prevSweep() + fl->prevSweep() ); total.set_beforeSweep(total.beforeSweep() + fl->beforeSweep()); total.set_count( total.count() + fl->count() ); total.set_coalBirths( total.coalBirths() + fl->coalBirths() ); total.set_coalDeaths( total.coalDeaths() + fl->coalDeaths() ); total.set_splitBirths(total.splitBirths() + fl->splitBirths()); total.set_splitDeaths(total.splitDeaths() + fl->splitDeaths()); } total.print_on(gclog_or_tty, "TOTAL"); gclog_or_tty->print_cr("Total free in indexed lists " SIZE_FORMAT " words", totalFree); gclog_or_tty->print("growth: %8.5f deficit: %8.5f\n", (double)(total.splitBirths()+total.coalBirths()-total.splitDeaths()-total.coalDeaths())/ (total.prevSweep() != 0 ? (double)total.prevSweep() : 1.0), (double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0)); _dictionary->printDictCensus(); } // Return the next displaced header, incrementing the pointer and // recycling spool area as necessary. markOop PromotionInfo::nextDisplacedHeader() { assert(_spoolHead != NULL, "promotionInfo inconsistency"); assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex, "Empty spool space: no displaced header can be fetched"); assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?"); markOop hdr = _spoolHead->displacedHdr[_firstIndex]; // Spool forward if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block // forward to next block, recycling this block into spare spool buffer SpoolBlock* tmp = _spoolHead->nextSpoolBlock; assert(_spoolHead != _spoolTail, "Spooling storage mix-up"); _spoolHead->nextSpoolBlock = _spareSpool; _spareSpool = _spoolHead; _spoolHead = tmp; _firstIndex = 1; NOT_PRODUCT( if (_spoolHead == NULL) { // all buffers fully consumed assert(_spoolTail == NULL && _nextIndex == 1, "spool buffers processing inconsistency"); } ) } return hdr; } void PromotionInfo::track(PromotedObject* trackOop) { track(trackOop, oop(trackOop)->klass()); } void PromotionInfo::track(PromotedObject* trackOop, klassOop klassOfOop) { // make a copy of header as it may need to be spooled markOop mark = oop(trackOop)->mark(); trackOop->clearNext(); if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) { // save non-prototypical header, and mark oop saveDisplacedHeader(mark); trackOop->setDisplacedMark(); } else { // we'd like to assert something like the following: // assert(mark == markOopDesc::prototype(), "consistency check"); // ... but the above won't work because the age bits have not (yet) been // cleared. The remainder of the check would be identical to the // condition checked in must_be_preserved() above, so we don't really // have anything useful to check here! } if (_promoTail != NULL) { assert(_promoHead != NULL, "List consistency"); _promoTail->setNext(trackOop); _promoTail = trackOop; } else { assert(_promoHead == NULL, "List consistency"); _promoHead = _promoTail = trackOop; } // Mask as newly promoted, so we can skip over such objects // when scanning dirty cards assert(!trackOop->hasPromotedMark(), "Should not have been marked"); trackOop->setPromotedMark(); } // Save the given displaced header, incrementing the pointer and // obtaining more spool area as necessary. void PromotionInfo::saveDisplacedHeader(markOop hdr) { assert(_spoolHead != NULL && _spoolTail != NULL, "promotionInfo inconsistency"); assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?"); _spoolTail->displacedHdr[_nextIndex] = hdr; // Spool forward if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block // get a new spooling block assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list"); _splice_point = _spoolTail; // save for splicing _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ... // ... but will attempt filling before next promotion attempt _nextIndex = 1; } } // Ensure that spooling space exists. Return false if spooling space // could not be obtained. bool PromotionInfo::ensure_spooling_space_work() { assert(!has_spooling_space(), "Only call when there is no spooling space"); // Try and obtain more spooling space SpoolBlock* newSpool = getSpoolBlock(); assert(newSpool == NULL || (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL), "getSpoolBlock() sanity check"); if (newSpool == NULL) { return false; } _nextIndex = 1; if (_spoolTail == NULL) { _spoolTail = newSpool; if (_spoolHead == NULL) { _spoolHead = newSpool; _firstIndex = 1; } else { assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL, "Splice point invariant"); // Extra check that _splice_point is connected to list #ifdef ASSERT { SpoolBlock* blk = _spoolHead; for (; blk->nextSpoolBlock != NULL; blk = blk->nextSpoolBlock); assert(blk != NULL && blk == _splice_point, "Splice point incorrect"); } #endif // ASSERT _splice_point->nextSpoolBlock = newSpool; } } else { assert(_spoolHead != NULL, "spool list consistency"); _spoolTail->nextSpoolBlock = newSpool; _spoolTail = newSpool; } return true; } // Get a free spool buffer from the free pool, getting a new block // from the heap if necessary. SpoolBlock* PromotionInfo::getSpoolBlock() { SpoolBlock* res; if ((res = _spareSpool) != NULL) { _spareSpool = _spareSpool->nextSpoolBlock; res->nextSpoolBlock = NULL; } else { // spare spool exhausted, get some from heap res = (SpoolBlock*)(space()->allocateScratch(refillSize())); if (res != NULL) { res->init(); } } assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition"); return res; } void PromotionInfo::startTrackingPromotions() { assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex, "spooling inconsistency?"); _firstIndex = _nextIndex = 1; _tracking = true; } void PromotionInfo::stopTrackingPromotions() { assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex, "spooling inconsistency?"); _firstIndex = _nextIndex = 1; _tracking = false; } // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex> // points to the next slot available for filling. // The set of slots holding displaced headers are then all those in the // right-open interval denoted by: // // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> ) // // When _spoolTail is NULL, then the set of slots with displaced headers // is all those starting at the slot <_spoolHead, _firstIndex> and // going up to the last slot of last block in the linked list. // In this lartter case, _splice_point points to the tail block of // this linked list of blocks holding displaced headers. void PromotionInfo::verify() const { // Verify the following: // 1. the number of displaced headers matches the number of promoted // objects that have displaced headers // 2. each promoted object lies in this space debug_only( PromotedObject* junk = NULL; assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()), "Offset of PromotedObject::_next is expected to align with " " the OopDesc::_mark within OopDesc"); ) // FIXME: guarantee???? guarantee(_spoolHead == NULL || _spoolTail != NULL || _splice_point != NULL, "list consistency"); guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency"); // count the number of objects with displaced headers size_t numObjsWithDisplacedHdrs = 0; for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) { guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment"); // the last promoted object may fail the mark() != NULL test of is_oop(). guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop"); if (curObj->hasDisplacedMark()) { numObjsWithDisplacedHdrs++; } } // Count the number of displaced headers size_t numDisplacedHdrs = 0; for (SpoolBlock* curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL; curSpool = curSpool->nextSpoolBlock) { // the first entry is just a self-pointer; indices 1 through // bufferSize - 1 are occupied (thus, bufferSize - 1 slots). guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr, "first entry of displacedHdr should be self-referential"); numDisplacedHdrs += curSpool->bufferSize - 1; } guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0), "internal consistency"); guarantee(_spoolTail != NULL || _nextIndex == 1, "Inconsistency between _spoolTail and _nextIndex"); // We overcounted (_firstIndex-1) worth of slots in block // _spoolHead and we undercounted (_nextIndex-1) worth of // slots in block _spoolTail. We make an appropriate // adjustment by subtracting the first and adding the // second: - (_firstIndex - 1) + (_nextIndex - 1) numDisplacedHdrs += (_nextIndex - _firstIndex); guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count"); } CFLS_LAB::CFLS_LAB(CompactibleFreeListSpace* cfls) : _cfls(cfls) { _blocks_to_claim = CMSParPromoteBlocksToClaim; for (size_t i = CompactibleFreeListSpace::IndexSetStart; i < CompactibleFreeListSpace::IndexSetSize; i += CompactibleFreeListSpace::IndexSetStride) { _indexedFreeList[i].set_size(i); } } HeapWord* CFLS_LAB::alloc(size_t word_sz) { FreeChunk* res; word_sz = _cfls->adjustObjectSize(word_sz); if (word_sz >= CompactibleFreeListSpace::IndexSetSize) { // This locking manages sync with other large object allocations. MutexLockerEx x(_cfls->parDictionaryAllocLock(), Mutex::_no_safepoint_check_flag); res = _cfls->getChunkFromDictionaryExact(word_sz); if (res == NULL) return NULL; } else { FreeList* fl = &_indexedFreeList[word_sz]; bool filled = false; //TRAP if (fl->count() == 0) { bool filled = true; //TRAP // Attempt to refill this local free list. _cfls->par_get_chunk_of_blocks(word_sz, _blocks_to_claim, fl); // If it didn't work, give up. if (fl->count() == 0) return NULL; } res = fl->getChunkAtHead(); assert(res != NULL, "Why was count non-zero?"); } res->markNotFree(); assert(!res->isFree(), "shouldn't be marked free"); assert(oop(res)->klass_or_null() == NULL, "should look uninitialized"); // mangle a just allocated object with a distinct pattern. debug_only(res->mangleAllocated(word_sz)); return (HeapWord*)res; } void CFLS_LAB::retire() { for (size_t i = CompactibleFreeListSpace::IndexSetStart; i < CompactibleFreeListSpace::IndexSetSize; i += CompactibleFreeListSpace::IndexSetStride) { if (_indexedFreeList[i].count() > 0) { MutexLockerEx x(_cfls->_indexedFreeListParLocks[i], Mutex::_no_safepoint_check_flag); _cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]); // Reset this list. _indexedFreeList[i] = FreeList(); _indexedFreeList[i].set_size(i); } } } void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl) { assert(fl->count() == 0, "Precondition."); assert(word_sz < CompactibleFreeListSpace::IndexSetSize, "Precondition"); // We'll try all multiples of word_sz in the indexed set (starting with // word_sz itself), then try getting a big chunk and splitting it. int k = 1; size_t cur_sz = k * word_sz; bool found = false; while (cur_sz < CompactibleFreeListSpace::IndexSetSize && k == 1) { FreeList* gfl = &_indexedFreeList[cur_sz]; FreeList fl_for_cur_sz; // Empty. fl_for_cur_sz.set_size(cur_sz); { MutexLockerEx x(_indexedFreeListParLocks[cur_sz], Mutex::_no_safepoint_check_flag); if (gfl->count() != 0) { size_t nn = MAX2(n/k, (size_t)1); gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz); found = true; } } // Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1. if (found) { if (k == 1) { fl->prepend(&fl_for_cur_sz); } else { // Divide each block on fl_for_cur_sz up k ways. FreeChunk* fc; while ((fc = fl_for_cur_sz.getChunkAtHead()) != NULL) { // Must do this in reverse order, so that anybody attempting to // access the main chunk sees it as a single free block until we // change it. size_t fc_size = fc->size(); for (int i = k-1; i >= 0; i--) { FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz); ffc->setSize(word_sz); ffc->linkNext(NULL); ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads. // Above must occur before BOT is updated below. // splitting from the right, fc_size == (k - i + 1) * wordsize _bt.mark_block((HeapWord*)ffc, word_sz); fc_size -= word_sz; _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size()); _bt.verify_single_block((HeapWord*)fc, fc_size); _bt.verify_single_block((HeapWord*)ffc, ffc->size()); // Push this on "fl". fl->returnChunkAtHead(ffc); } // TRAP assert(fl->tail()->next() == NULL, "List invariant."); } } return; } k++; cur_sz = k * word_sz; } // Otherwise, we'll split a block from the dictionary. FreeChunk* fc = NULL; FreeChunk* rem_fc = NULL; size_t rem; { MutexLockerEx x(parDictionaryAllocLock(), Mutex::_no_safepoint_check_flag); while (n > 0) { fc = dictionary()->getChunk(MAX2(n * word_sz, _dictionary->minSize()), FreeBlockDictionary::atLeast); if (fc != NULL) { _bt.allocated((HeapWord*)fc, fc->size()); // update _unallocated_blk dictionary()->dictCensusUpdate(fc->size(), true /*split*/, false /*birth*/); break; } else { n--; } } if (fc == NULL) return; // Otherwise, split up that block. size_t nn = fc->size() / word_sz; n = MIN2(nn, n); rem = fc->size() - n * word_sz; // If there is a remainder, and it's too small, allocate one fewer. if (rem > 0 && rem < MinChunkSize) { n--; rem += word_sz; } // First return the remainder, if any. // Note that we hold the lock until we decide if we're going to give // back the remainder to the dictionary, since a contending allocator // may otherwise see the heap as empty. (We're willing to take that // hit if the block is a small block.) if (rem > 0) { size_t prefix_size = n * word_sz; rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size); rem_fc->setSize(rem); rem_fc->linkNext(NULL); rem_fc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads. // Above must occur before BOT is updated below. _bt.split_block((HeapWord*)fc, fc->size(), prefix_size); if (rem >= IndexSetSize) { returnChunkToDictionary(rem_fc); dictionary()->dictCensusUpdate(fc->size(), true /*split*/, true /*birth*/); rem_fc = NULL; } // Otherwise, return it to the small list below. } } // if (rem_fc != NULL) { MutexLockerEx x(_indexedFreeListParLocks[rem], Mutex::_no_safepoint_check_flag); _bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size()); _indexedFreeList[rem].returnChunkAtHead(rem_fc); smallSplitBirth(rem); } // Now do the splitting up. // Must do this in reverse order, so that anybody attempting to // access the main chunk sees it as a single free block until we // change it. size_t fc_size = n * word_sz; // All but first chunk in this loop for (ssize_t i = n-1; i > 0; i--) { FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz); ffc->setSize(word_sz); ffc->linkNext(NULL); ffc->linkPrev(NULL); // Mark as a free block for other (parallel) GC threads. // Above must occur before BOT is updated below. // splitting from the right, fc_size == (n - i + 1) * wordsize _bt.mark_block((HeapWord*)ffc, word_sz); fc_size -= word_sz; _bt.verify_not_unallocated((HeapWord*)ffc, ffc->size()); _bt.verify_single_block((HeapWord*)ffc, ffc->size()); _bt.verify_single_block((HeapWord*)fc, fc_size); // Push this on "fl". fl->returnChunkAtHead(ffc); } // First chunk fc->setSize(word_sz); fc->linkNext(NULL); fc->linkPrev(NULL); _bt.verify_not_unallocated((HeapWord*)fc, fc->size()); _bt.verify_single_block((HeapWord*)fc, fc->size()); fl->returnChunkAtHead(fc); { MutexLockerEx x(_indexedFreeListParLocks[word_sz], Mutex::_no_safepoint_check_flag); ssize_t new_births = _indexedFreeList[word_sz].splitBirths() + n; _indexedFreeList[word_sz].set_splitBirths(new_births); ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n; _indexedFreeList[word_sz].set_surplus(new_surplus); } // TRAP assert(fl->tail()->next() == NULL, "List invariant."); } // Set up the space's par_seq_tasks structure for work claiming // for parallel rescan. See CMSParRemarkTask where this is currently used. // XXX Need to suitably abstract and generalize this and the next // method into one. void CompactibleFreeListSpace:: initialize_sequential_subtasks_for_rescan(int n_threads) { // The "size" of each task is fixed according to rescan_task_size. assert(n_threads > 0, "Unexpected n_threads argument"); const size_t task_size = rescan_task_size(); size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size; assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect"); assert(n_tasks == 0 || ((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) && (used_region().start() + n_tasks*task_size >= used_region().end())), "n_tasks calculation incorrect"); SequentialSubTasksDone* pst = conc_par_seq_tasks(); assert(!pst->valid(), "Clobbering existing data?"); pst->set_par_threads(n_threads); pst->set_n_tasks((int)n_tasks); } // Set up the space's par_seq_tasks structure for work claiming // for parallel concurrent marking. See CMSConcMarkTask where this is currently used. void CompactibleFreeListSpace:: initialize_sequential_subtasks_for_marking(int n_threads, HeapWord* low) { // The "size" of each task is fixed according to rescan_task_size. assert(n_threads > 0, "Unexpected n_threads argument"); const size_t task_size = marking_task_size(); assert(task_size > CardTableModRefBS::card_size_in_words && (task_size % CardTableModRefBS::card_size_in_words == 0), "Otherwise arithmetic below would be incorrect"); MemRegion span = _gen->reserved(); if (low != NULL) { if (span.contains(low)) { // Align low down to a card boundary so that // we can use block_offset_careful() on span boundaries. HeapWord* aligned_low = (HeapWord*)align_size_down((uintptr_t)low, CardTableModRefBS::card_size); // Clip span prefix at aligned_low span = span.intersection(MemRegion(aligned_low, span.end())); } else if (low > span.end()) { span = MemRegion(low, low); // Null region } // else use entire span } assert(span.is_empty() || ((uintptr_t)span.start() % CardTableModRefBS::card_size == 0), "span should start at a card boundary"); size_t n_tasks = (span.word_size() + task_size - 1)/task_size; assert((n_tasks == 0) == span.is_empty(), "Inconsistency"); assert(n_tasks == 0 || ((span.start() + (n_tasks - 1)*task_size < span.end()) && (span.start() + n_tasks*task_size >= span.end())), "n_tasks calculation incorrect"); SequentialSubTasksDone* pst = conc_par_seq_tasks(); assert(!pst->valid(), "Clobbering existing data?"); pst->set_par_threads(n_threads); pst->set_n_tasks((int)n_tasks); }