# HG changeset patch # User tonyp # Date 1237169018 14400 # Node ID 6c4cea9bfa1150b3424a5192e76431d5f86c60c6 # Parent fe24415002812ab6abd4fd64817536fc19acce58 6604422: G1: re-use half-promoted regions 6728271: G1: Cleanup G1CollectedHeap::get_gc_alloc_regions() Summary: It allows the last half-full region to be allocated to during a GC to be reused during the next GC. Reviewed-by: apetrusenko, jcoomes diff -r fe2441500281 -r 6c4cea9bfa11 src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp --- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Fri Mar 13 17:06:44 2009 -0700 +++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Sun Mar 15 22:03:38 2009 -0400 @@ -786,6 +786,12 @@ } } +void G1CollectedHeap::abandon_gc_alloc_regions() { + // first, make sure that the GC alloc region list is empty (it should!) + assert(_gc_alloc_region_list == NULL, "invariant"); + release_gc_alloc_regions(true /* totally */); +} + class PostMCRemSetClearClosure: public HeapRegionClosure { ModRefBarrierSet* _mr_bs; public: @@ -914,6 +920,7 @@ // Make sure we'll choose a new allocation region afterwards. abandon_cur_alloc_region(); + abandon_gc_alloc_regions(); assert(_cur_alloc_region == NULL, "Invariant."); g1_rem_set()->as_HRInto_G1RemSet()->cleanupHRRS(); tear_down_region_lists(); @@ -1306,7 +1313,7 @@ } void G1CollectedHeap::shrink(size_t shrink_bytes) { - release_gc_alloc_regions(); + release_gc_alloc_regions(true /* totally */); tear_down_region_lists(); // We will rebuild them in a moment. shrink_helper(shrink_bytes); rebuild_region_lists(); @@ -1345,8 +1352,7 @@ _gc_time_stamp(0), _surviving_young_words(NULL), _in_cset_fast_test(NULL), - _in_cset_fast_test_base(NULL) -{ + _in_cset_fast_test_base(NULL) { _g1h = this; // To catch bugs. if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { vm_exit_during_initialization("Failed necessary allocation."); @@ -1371,9 +1377,19 @@ } for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { - _gc_alloc_regions[ap] = NULL; - _gc_alloc_region_counts[ap] = 0; - } + _gc_alloc_regions[ap] = NULL; + _gc_alloc_region_counts[ap] = 0; + _retained_gc_alloc_regions[ap] = NULL; + // by default, we do not retain a GC alloc region for each ap; + // we'll override this, when appropriate, below + _retain_gc_alloc_region[ap] = false; + } + + // We will try to remember the last half-full tenured region we + // allocated to at the end of a collection so that we can re-use it + // during the next collection. + _retain_gc_alloc_region[GCAllocForTenured] = true; + guarantee(_task_queues != NULL, "task_queues allocation failure."); } @@ -2644,7 +2660,7 @@ popular_region->set_popular_pending(false); } - release_gc_alloc_regions(); + release_gc_alloc_regions(false /* totally */); cleanup_surviving_young_words(); @@ -2735,6 +2751,10 @@ void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) { assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose"); + // make sure we don't call set_gc_alloc_region() multiple times on + // the same region + assert(r == NULL || !r->is_gc_alloc_region(), + "shouldn't already be a GC alloc region"); HeapWord* original_top = NULL; if (r != NULL) original_top = r->top(); @@ -2851,23 +2871,55 @@ } void G1CollectedHeap::get_gc_alloc_regions() { + // First, let's check that the GC alloc region list is empty (it should) + assert(_gc_alloc_region_list == NULL, "invariant"); + for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { + assert(_gc_alloc_regions[ap] == NULL, "invariant"); + // Create new GC alloc regions. - HeapRegion* alloc_region = _gc_alloc_regions[ap]; - // Clear this alloc region, so that in case it turns out to be - // unacceptable, we end up with no allocation region, rather than a bad - // one. - _gc_alloc_regions[ap] = NULL; - if (alloc_region == NULL || alloc_region->in_collection_set()) { - // Can't re-use old one. Allocate a new one. + HeapRegion* alloc_region = _retained_gc_alloc_regions[ap]; + _retained_gc_alloc_regions[ap] = NULL; + + if (alloc_region != NULL) { + assert(_retain_gc_alloc_region[ap], "only way to retain a GC region"); + + // let's make sure that the GC alloc region is not tagged as such + // outside a GC operation + assert(!alloc_region->is_gc_alloc_region(), "sanity"); + + if (alloc_region->in_collection_set() || + alloc_region->top() == alloc_region->end() || + alloc_region->top() == alloc_region->bottom()) { + // we will discard the current GC alloc region if it's in the + // collection set (it can happen!), if it's already full (no + // point in using it), or if it's empty (this means that it + // was emptied during a cleanup and it should be on the free + // list now). + + alloc_region = NULL; + } + } + + if (alloc_region == NULL) { + // we will get a new GC alloc region alloc_region = newAllocRegionWithExpansion(ap, 0); } + if (alloc_region != NULL) { + assert(_gc_alloc_regions[ap] == NULL, "pre-condition"); set_gc_alloc_region(ap, alloc_region); } + + assert(_gc_alloc_regions[ap] == NULL || + _gc_alloc_regions[ap]->is_gc_alloc_region(), + "the GC alloc region should be tagged as such"); + assert(_gc_alloc_regions[ap] == NULL || + _gc_alloc_regions[ap] == _gc_alloc_region_list, + "the GC alloc region should be the same as the GC alloc list head"); } // Set alternative regions for allocation purposes that have reached - // thier limit. + // their limit. for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(ap); if (_gc_alloc_regions[ap] == NULL && alt_purpose != ap) { @@ -2877,27 +2929,55 @@ assert(check_gc_alloc_regions(), "alloc regions messed up"); } -void G1CollectedHeap::release_gc_alloc_regions() { +void G1CollectedHeap::release_gc_alloc_regions(bool totally) { // We keep a separate list of all regions that have been alloc regions in - // the current collection pause. Forget that now. + // the current collection pause. Forget that now. This method will + // untag the GC alloc regions and tear down the GC alloc region + // list. It's desirable that no regions are tagged as GC alloc + // outside GCs. forget_alloc_region_list(); // The current alloc regions contain objs that have survived // collection. Make them no longer GC alloc regions. for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { HeapRegion* r = _gc_alloc_regions[ap]; - if (r != NULL && r->is_empty()) { - { + _retained_gc_alloc_regions[ap] = NULL; + + if (r != NULL) { + // we retain nothing on _gc_alloc_regions between GCs + set_gc_alloc_region(ap, NULL); + _gc_alloc_region_counts[ap] = 0; + + if (r->is_empty()) { + // we didn't actually allocate anything in it; let's just put + // it on the free list MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag); r->set_zero_fill_complete(); put_free_region_on_list_locked(r); + } else if (_retain_gc_alloc_region[ap] && !totally) { + // retain it so that we can use it at the beginning of the next GC + _retained_gc_alloc_regions[ap] = r; } } - // set_gc_alloc_region will also NULLify all aliases to the region - set_gc_alloc_region(ap, NULL); - _gc_alloc_region_counts[ap] = 0; - } -} + } +} + +#ifndef PRODUCT +// Useful for debugging + +void G1CollectedHeap::print_gc_alloc_regions() { + gclog_or_tty->print_cr("GC alloc regions"); + for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { + HeapRegion* r = _gc_alloc_regions[ap]; + if (r == NULL) { + gclog_or_tty->print_cr(" %2d : "PTR_FORMAT, ap, NULL); + } else { + gclog_or_tty->print_cr(" %2d : "PTR_FORMAT" "SIZE_FORMAT, + ap, r->bottom(), r->used()); + } + } +} +#endif // PRODUCT void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { _drain_in_progress = false; diff -r fe2441500281 -r 6c4cea9bfa11 src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp --- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp Fri Mar 13 17:06:44 2009 -0700 +++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp Sun Mar 15 22:03:38 2009 -0400 @@ -172,7 +172,6 @@ NumAPIs = HeapRegion::MaxAge }; - // The one and only G1CollectedHeap, so static functions can find it. static G1CollectedHeap* _g1h; @@ -217,11 +216,20 @@ // Postcondition: cur_alloc_region == NULL. void abandon_cur_alloc_region(); + void abandon_gc_alloc_regions(); // The to-space memory regions into which objects are being copied during // a GC. HeapRegion* _gc_alloc_regions[GCAllocPurposeCount]; size_t _gc_alloc_region_counts[GCAllocPurposeCount]; + // These are the regions, one per GCAllocPurpose, that are half-full + // at the end of a collection and that we want to reuse during the + // next collection. + HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount]; + // This specifies whether we will keep the last half-full region at + // the end of a collection so that it can be reused during the next + // collection (this is specified per GCAllocPurpose) + bool _retain_gc_alloc_region[GCAllocPurposeCount]; // A list of the regions that have been set to be alloc regions in the // current collection. @@ -589,8 +597,21 @@ // Ensure that the relevant gc_alloc regions are set. void get_gc_alloc_regions(); - // We're done with GC alloc regions; release them, as appropriate. - void release_gc_alloc_regions(); + // We're done with GC alloc regions. We are going to tear down the + // gc alloc list and remove the gc alloc tag from all the regions on + // that list. However, we will also retain the last (i.e., the one + // that is half-full) GC alloc region, per GCAllocPurpose, for + // possible reuse during the next collection, provided + // _retain_gc_alloc_region[] indicates that it should be the + // case. Said regions are kept in the _retained_gc_alloc_regions[] + // array. If the parameter totally is set, we will not retain any + // regions, irrespective of what _retain_gc_alloc_region[] + // indicates. + void release_gc_alloc_regions(bool totally); +#ifndef PRODUCT + // Useful for debugging. + void print_gc_alloc_regions(); +#endif // !PRODUCT // ("Weak") Reference processing support ReferenceProcessor* _ref_processor; diff -r fe2441500281 -r 6c4cea9bfa11 src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp --- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp Fri Mar 13 17:06:44 2009 -0700 +++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp Sun Mar 15 22:03:38 2009 -0400 @@ -1087,6 +1087,7 @@ assert(_g1->used_regions() == _g1->recalculate_used_regions(), "sanity"); + assert(_g1->used() == _g1->recalculate_used(), "sanity"); double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0; _all_stop_world_times_ms->add(s_w_t_ms);