truffle: src/share/vm/memory/heap.cpp comparison

comparison src/share/vm/memory/heap.cpp @ 14704:b51e29501f30

Merged with jdk9/dev/hotspot changeset 9486a41de3b7

author	twisti
date	Tue, 18 Mar 2014 20:19:10 -0700
parents	d8041d695d19 480b0109db65
children	92aa6797d639

comparison

equal deleted inserted replaced

-:8f483e200405
+:b51e29501f30
 _segment_size                 = 0;
 _log2_segment_size            = 0;
 _next_segment                 = 0;
 _freelist                     = NULL;
 _freelist_segments            = 0;
+_freelist_length              = 0;
 }
 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) {
 assert(0   <= beg && beg <  _number_of_committed_segments, "interval begin out of bounds");
 assert(beg <  end && end <= _number_of_committed_segments, "interval end   out of bounds");
 // setup _segmap pointers for faster indexing
 address p = (address)_segmap.low() + beg;
 address q = (address)_segmap.low() + end;
 // initialize interval
-while (p < q) *p++ = 0xFF;
+while (p < q) *p++ = free_sentinel;
 }
 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) {
 assert(0   <= beg && beg <  _number_of_committed_segments, "interval begin out of bounds");
 address q = (address)_segmap.low() + end;
 // initialize interval
 int i = 0;
 while (p < q) {
 *p++ = i++;
-if (i == 0xFF) i = 1;
+if (i == free_sentinel) i = 1;
 }
 }
 static size_t align_to_page_size(size_t size) {
 assert(_segmap.reserved_size()  >= _segmap.committed_size()     , "just checking");
 // initialize remaining instance variables
 clear();
 return true;
-}
-void CodeHeap::release() {
-Unimplemented();
 }
 bool CodeHeap::expand_by(size_t size) {
 // expand _memory space
 _number_of_committed_segments = size_to_segments(_memory.committed_size());
 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
 // expand _segmap space
 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
-if (ds > 0) {
+if ((ds > 0) && !_segmap.expand_by(ds)) {
-if (!_segmap.expand_by(ds)) return false;
+return false;
 }
 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
 // initialize additional segmap entries
 mark_segmap_as_free(i, _number_of_committed_segments);
 }
 return true;
 }
-void CodeHeap::shrink_by(size_t size) {
-Unimplemented();
-}
 void CodeHeap::clear() {
 _next_segment = 0;
 mark_segmap_as_free(0, _number_of_committed_segments);
 }
 void* CodeHeap::allocate(size_t instance_size, bool is_critical) {
-size_t number_of_segments = size_to_segments(instance_size + sizeof(HeapBlock));
+size_t number_of_segments = size_to_segments(instance_size + header_size());
 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
 // First check if we can satisfy request from freelist
-debug_only(verify());
+NOT_PRODUCT(verify());
 HeapBlock* block = search_freelist(number_of_segments, is_critical);
-debug_only(if (VerifyCodeCacheOften) verify());
+NOT_PRODUCT(verify());
 if (block != NULL) {
 assert(block->length() >= number_of_segments && block->length() < number_of_segments + CodeCacheMinBlockLength, "sanity check");
 assert(!block->free(), "must be marked free");
-#ifdef ASSERT
+DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size));
-memset((void *)block->allocated_space(), badCodeHeapNewVal, instance_size);
-#endif
 return block->allocated_space();
 }
 // Ensure minimum size for allocation to the heap.
-if (number_of_segments < CodeCacheMinBlockLength) {
+number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
-number_of_segments = CodeCacheMinBlockLength;
-}
 if (!is_critical) {
 // Make sure the allocation fits in the unallocated heap without using
 // the CodeCacheMimimumFreeSpace that is reserved for critical allocations.
 if (segments_to_size(number_of_segments) > (heap_unallocated_capacity() - CodeCacheMinimumFreeSpace)) {
 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
 HeapBlock* b =  block_at(_next_segment);
 b->initialize(number_of_segments);
 _next_segment += number_of_segments;
-#ifdef ASSERT
+DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size));
-memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size);
-#endif
 return b->allocated_space();
 } else {
 return NULL;
 }
 }
 void CodeHeap::deallocate(void* p) {
 assert(p == find_start(p), "illegal deallocation");
 // Find start of HeapBlock
 HeapBlock* b = (((HeapBlock *)p) - 1);
 assert(b->allocated_space() == p, "sanity check");
-#ifdef ASSERT
+DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal,
-memset((void *)b->allocated_space(),
+segments_to_size(b->length()) - sizeof(HeapBlock)));
-badCodeHeapFreeVal,
-segments_to_size(b->length()) - sizeof(HeapBlock));
-#endif
 add_to_freelist(b);
+NOT_PRODUCT(verify());
-debug_only(if (VerifyCodeCacheOften) verify());
+}
-}
+/**
+* Uses segment map to find the the start (header) of a nmethod. This works as follows:
+* The memory of the code cache is divided into 'segments'. The size of a segment is
+* determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only
+* happen at segment boundaries. A pointer in the code cache can be mapped to a segment
+* by calling segment_for(addr). Each time memory is requested from the code cache,
+* the segmap is updated accordingly. See the following example, which illustrates the
+* state of code cache and the segment map: (seg -> segment, nm ->nmethod)
+*
+*          code cache          segmap
+*         -----------        ---------
+* seg 1   | nm 1    |   ->   | 0     |
+* seg 2   | nm 1    |   ->   | 1     |
+* ...     | nm 1    |   ->   | ..    |
+* seg m   | nm 2    |   ->   | 0     |
+* seg m+1 | nm 2    |   ->   | 1     |
+* ...     | nm 2    |   ->   | 2     |
+* ...     | nm 2    |   ->   | ..    |
+* ...     | nm 2    |   ->   | 0xFE  |
+* seg m+n | nm 2    |   ->   | 1     |
+* ...     | nm 2    |   ->   |       |
+*
+* A value of '0' in the segmap indicates that this segment contains the beginning of
+* an nmethod. Let's walk through a simple example: If we want to find the start of
+* an nmethod that falls into seg 2, we read the value of the segmap[2]. The value
+* is an offset that points to the segment that contains the start of the nmethod.
+* Another example: If we want to get the start of nm 2, and we happen to get a pointer
+* that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to
+* do one more read of the segmap[m+n-1] to finally get the segment header.
+*/
 void* CodeHeap::find_start(void* p) const {
 if (!contains(p)) {
 return NULL;
 }
-size_t i = segment_for(p);
+size_t seg_idx = segment_for(p);
-address b = (address)_segmap.low();
+address seg_map = (address)_segmap.low();
-if (b[i] == 0xFF) {
+if (is_segment_unused(seg_map[seg_idx])) {
 return NULL;
 }
-while (b[i] > 0) i -= (int)b[i];
+while (seg_map[seg_idx] > 0) {
-HeapBlock* h = block_at(i);
+seg_idx -= (int)seg_map[seg_idx];
+}
+HeapBlock* h = block_at(seg_idx);
 if (h->free()) {
 return NULL;
 }
 return h->allocated_space();
 }
 // equal to alignment_offset (mod alignment_unit).
 return sizeof(HeapBlock) & (_segment_size - 1);
 }
 // Finds the next free heapblock. If the current one is free, that it returned
-void* CodeHeap::next_free(HeapBlock *b) const {
+void* CodeHeap::next_free(HeapBlock* b) const {
 // Since free blocks are merged, there is max. on free block
 // between two used ones
 if (b != NULL && b->free()) b = next_block(b);
 assert(b == NULL || !b->free(), "must be in use or at end of heap");
 return (b == NULL) ? NULL : b->allocated_space();
 if (_next_segment > 0)
 return block_at(0);
 return NULL;
 }
-HeapBlock *CodeHeap::block_start(void *q) const {
+HeapBlock* CodeHeap::block_start(void* q) const {
 HeapBlock* b = (HeapBlock*)find_start(q);
 if (b == NULL) return NULL;
 return b - 1;
 }
 size_t CodeHeap::max_capacity() const {
 return _memory.reserved_size();
 }
+int CodeHeap::allocated_segments() const {
+return (int)_next_segment;
+}
 size_t CodeHeap::allocated_capacity() const {
 // size of used heap - size on freelist
 return segments_to_size(_next_segment - _freelist_segments);
 }
 return segments_to_size(_number_of_reserved_segments - _next_segment);
 }
 // Free list management
-FreeBlock *CodeHeap::following_block(FreeBlock *b) {
+FreeBlock* CodeHeap::following_block(FreeBlock *b) {
 return (FreeBlock*)(((address)b) + _segment_size * b->length());
 }
 // Inserts block b after a
 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
 merge_right(b); // Try to make b bigger
 merge_right(a); // Try to make a include b
 }
 // Try to merge this block with the following block
-void CodeHeap::merge_right(FreeBlock *a) {
+bool CodeHeap::merge_right(FreeBlock* a) {
 assert(a->free(), "must be a free block");
 if (following_block(a) == a->link()) {
 assert(a->link() != NULL && a->link()->free(), "must be free too");
 // Update block a to include the following block
 a->set_length(a->length() + a->link()->length());
 a->set_link(a->link()->link());
 // Update find_start map
 size_t beg = segment_for(a);
 mark_segmap_as_used(beg, beg + a->length());
-}
+_freelist_length--;
-}
+return true;
+}
-void CodeHeap::add_to_freelist(HeapBlock *a) {
+return false;
+}
+void CodeHeap::add_to_freelist(HeapBlock* a) {
 FreeBlock* b = (FreeBlock*)a;
+_freelist_length++;
 assert(b != _freelist, "cannot be removed twice");
 // Mark as free and update free space count
 _freelist_segments += b->length();
 b->set_free();
 _freelist = b;
 b->set_link(NULL);
 return;
 }
-// Scan for right place to put into list. List
+// Since the freelist is ordered (smaller addresses -> larger addresses) and the
-// is sorted by increasing addresses
+// element we want to insert into the freelist has a smaller address than the first
-FreeBlock* prev = NULL;
+// element, we can simply add 'b' as the first element and we are done.
-FreeBlock* cur  = _freelist;
+if (b < _freelist) {
-while(cur != NULL && cur < b) {
-assert(prev == NULL || prev < cur, "must be ordered");
-prev = cur;
-cur  = cur->link();
-}
-assert( (prev == NULL && b < _freelist) ||
-(prev < b && (cur == NULL || b < cur)), "list must be ordered");
-if (prev == NULL) {
 // Insert first in list
 b->set_link(_freelist);
 _freelist = b;
 merge_right(_freelist);
-} else {
+return;
-insert_after(prev, b);
+}
-}
-}
+// Scan for right place to put into list. List
+// is sorted by increasing addresses
-// Search freelist for an entry on the list with the best fit
+FreeBlock* prev = _freelist;
-// Return NULL if no one was found
+FreeBlock* cur  = _freelist->link();
+while(cur != NULL && cur < b) {
+assert(prev < cur, "Freelist must be ordered");
+prev = cur;
+cur  = cur->link();
+}
+assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
+insert_after(prev, b);
+}
+/**
+* Search freelist for an entry on the list with the best fit.
+* @return NULL, if no one was found
+*/
 FreeBlock* CodeHeap::search_freelist(size_t length, bool is_critical) {
-FreeBlock *best_block = NULL;
+FreeBlock* found_block = NULL;
-FreeBlock *best_prev  = NULL;
+FreeBlock* found_prev  = NULL;
-size_t best_length = 0;
+size_t     found_length = 0;
-// Search for smallest block which is bigger than length
+FreeBlock* prev = NULL;
-FreeBlock *prev = NULL;
+FreeBlock* cur = _freelist;
-FreeBlock *cur = _freelist;
+const size_t critical_boundary = (size_t)high_boundary() - CodeCacheMinimumFreeSpace;
+// Search for first block that fits
 while(cur != NULL) {
-size_t l = cur->length();
+if (cur->length() >= length) {
-if (l >= length && (best_block == NULL || best_length > l)) {
 // Non critical allocations are not allowed to use the last part of the code heap.
-if (!is_critical) {
+// Make sure the end of the allocation doesn't cross into the last part of the code heap.
-// Make sure the end of the allocation doesn't cross into the last part of the code heap
+if (!is_critical && (((size_t)cur + length) > critical_boundary)) {
-if (((size_t)cur + length) > ((size_t)high_boundary() - CodeCacheMinimumFreeSpace)) {
+// The freelist is sorted by address - if one fails, all consecutive will also fail.
-// the freelist is sorted by address - if one fails, all consecutive will also fail.
+break;
-break;
-}
 }
+// Remember block, its previous element, and its length
-// Remember best block, its previous element, and its length
+found_block = cur;
-best_block = cur;
+found_prev  = prev;
-best_prev  = prev;
+found_length = found_block->length();
-best_length = best_block->length();
-}
+break;
+}
 // Next element in list
 prev = cur;
 cur  = cur->link();
 }
-if (best_block == NULL) {
+if (found_block == NULL) {
 // None found
 return NULL;
 }
-assert((best_prev == NULL && _freelist == best_block ) ||
-(best_prev != NULL && best_prev->link() == best_block), "sanity check");
 // Exact (or at least good enough) fit. Remove from list.
 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
-if (best_length < length + CodeCacheMinBlockLength) {
+if (found_length - length < CodeCacheMinBlockLength) {
-length = best_length;
+_freelist_length--;
-if (best_prev == NULL) {
+length = found_length;
-assert(_freelist == best_block, "sanity check");
+if (found_prev == NULL) {
+assert(_freelist == found_block, "sanity check");
 _freelist = _freelist->link();
 } else {
+assert((found_prev->link() == found_block), "sanity check");
 // Unmap element
-best_prev->set_link(best_block->link());
+found_prev->set_link(found_block->link());
 }
 } else {
 // Truncate block and return a pointer to the following block
-best_block->set_length(best_length - length);
-best_block = following_block(best_block);
 // Set used bit and length on new block
-size_t beg = segment_for(best_block);
+found_block->set_length(found_length - length);
+found_block = following_block(found_block);
+size_t beg = segment_for(found_block);
 mark_segmap_as_used(beg, beg + length);
-best_block->set_length(length);
+found_block->set_length(length);
 }
-best_block->set_used();
+found_block->set_used();
 _freelist_segments -= length;
-return best_block;
+return found_block;
 }
 //----------------------------------------------------------------------------
 // Non-product code
 void CodeHeap::print() {
 tty->print_cr("The Heap");
 }
+void CodeHeap::verify() {
+if (VerifyCodeCache) {
+size_t len = 0;
+int count = 0;
+for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
+len += b->length();
+count++;
+// Check if we have merged all free blocks
+assert(merge_right(b) == false, "Missed merging opportunity");
+}
+// Verify that freelist contains the right amount of free space
+assert(len == _freelist_segments, "wrong freelist");
+for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
+if (h->free()) count--;
+}
+// Verify that the freelist contains the same number of blocks
+// than free blocks found on the full list.
+assert(count == 0, "missing free blocks");
+// Verify that the number of free blocks is not out of hand.
+static int free_block_threshold = 10000;
+if (count > free_block_threshold) {
+warning("CodeHeap: # of free blocks > %d", free_block_threshold);
+// Double the warning limit
+free_block_threshold *= 2;
+}
+}
+}
 #endif
-void CodeHeap::verify() {
-// Count the number of blocks on the freelist, and the amount of space
-// represented.
-int count = 0;
-size_t len = 0;
-for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
-len += b->length();
-count++;
-}
-// Verify that freelist contains the right amount of free space
-//  guarantee(len == _freelist_segments, "wrong freelist");
-// Verify that the number of free blocks is not out of hand.
-static int free_block_threshold = 10000;
-if (count > free_block_threshold) {
-warning("CodeHeap: # of free blocks > %d", free_block_threshold);
-// Double the warning limit
-free_block_threshold *= 2;
-}
-// Verify that the freelist contains the same number of free blocks that is
-// found on the full list.
-for(HeapBlock *h = first_block(); h != NULL; h = next_block(h)) {
-if (h->free()) count--;
-}
-//  guarantee(count == 0, "missing free blocks");
-}

Mercurial > hg > truffle

comparison src/share/vm/memory/heap.cpp @ 14704:b51e29501f30