| /* |
| * Copyright (c) 2000, 2016, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #ifndef SHARE_VM_GC_SHARED_SPACE_INLINE_HPP |
| #define SHARE_VM_GC_SHARED_SPACE_INLINE_HPP |
| |
| #include "gc/serial/markSweep.inline.hpp" |
| #include "gc/shared/collectedHeap.hpp" |
| #include "gc/shared/generation.hpp" |
| #include "gc/shared/space.hpp" |
| #include "gc/shared/spaceDecorator.hpp" |
| #include "memory/universe.hpp" |
| #include "oops/oopsHierarchy.hpp" |
| #include "runtime/prefetch.inline.hpp" |
| #include "runtime/safepoint.hpp" |
| |
| inline HeapWord* Space::block_start(const void* p) { |
| return block_start_const(p); |
| } |
| |
| inline HeapWord* OffsetTableContigSpace::allocate(size_t size) { |
| HeapWord* res = ContiguousSpace::allocate(size); |
| if (res != NULL) { |
| _offsets.alloc_block(res, size); |
| } |
| return res; |
| } |
| |
| // Because of the requirement of keeping "_offsets" up to date with the |
| // allocations, we sequentialize these with a lock. Therefore, best if |
| // this is used for larger LAB allocations only. |
| inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) { |
| MutexLocker x(&_par_alloc_lock); |
| // This ought to be just "allocate", because of the lock above, but that |
| // ContiguousSpace::allocate asserts that either the allocating thread |
| // holds the heap lock or it is the VM thread and we're at a safepoint. |
| // The best I (dld) could figure was to put a field in ContiguousSpace |
| // meaning "locking at safepoint taken care of", and set/reset that |
| // here. But this will do for now, especially in light of the comment |
| // above. Perhaps in the future some lock-free manner of keeping the |
| // coordination. |
| HeapWord* res = ContiguousSpace::par_allocate(size); |
| if (res != NULL) { |
| _offsets.alloc_block(res, size); |
| } |
| return res; |
| } |
| |
| inline HeapWord* |
| OffsetTableContigSpace::block_start_const(const void* p) const { |
| return _offsets.block_start(p); |
| } |
| |
| size_t CompactibleSpace::obj_size(const HeapWord* addr) const { |
| return oop(addr)->size(); |
| } |
| |
| class DeadSpacer : StackObj { |
| size_t _allowed_deadspace_words; |
| bool _active; |
| CompactibleSpace* _space; |
| |
| public: |
| DeadSpacer(CompactibleSpace* space) : _space(space), _allowed_deadspace_words(0) { |
| size_t ratio = _space->allowed_dead_ratio(); |
| _active = ratio > 0; |
| |
| if (_active) { |
| assert(!UseG1GC, "G1 should not be using dead space"); |
| |
| // We allow some amount of garbage towards the bottom of the space, so |
| // we don't start compacting before there is a significant gain to be made. |
| // Occasionally, we want to ensure a full compaction, which is determined |
| // by the MarkSweepAlwaysCompactCount parameter. |
| if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) { |
| _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize; |
| } else { |
| _active = false; |
| } |
| } |
| } |
| |
| |
| bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) { |
| if (!_active) { |
| return false; |
| } |
| |
| size_t dead_length = pointer_delta(dead_end, dead_start); |
| if (_allowed_deadspace_words >= dead_length) { |
| _allowed_deadspace_words -= dead_length; |
| CollectedHeap::fill_with_object(dead_start, dead_length); |
| oop obj = oop(dead_start); |
| obj->set_mark(obj->mark()->set_marked()); |
| |
| assert(dead_length == (size_t)obj->size(), "bad filler object size"); |
| log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b", |
| p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize); |
| |
| return true; |
| } else { |
| _active = false; |
| return false; |
| } |
| } |
| |
| }; |
| |
| template <class SpaceType> |
| inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) { |
| // Compute the new addresses for the live objects and store it in the mark |
| // Used by universe::mark_sweep_phase2() |
| |
| // We're sure to be here before any objects are compacted into this |
| // space, so this is a good time to initialize this: |
| space->set_compaction_top(space->bottom()); |
| |
| if (cp->space == NULL) { |
| assert(cp->gen != NULL, "need a generation"); |
| assert(cp->threshold == NULL, "just checking"); |
| assert(cp->gen->first_compaction_space() == space, "just checking"); |
| cp->space = cp->gen->first_compaction_space(); |
| cp->threshold = cp->space->initialize_threshold(); |
| cp->space->set_compaction_top(cp->space->bottom()); |
| } |
| |
| HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to. |
| |
| DeadSpacer dead_spacer(space); |
| |
| HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object. |
| HeapWord* first_dead = NULL; // The first dead object. |
| |
| const intx interval = PrefetchScanIntervalInBytes; |
| |
| HeapWord* cur_obj = space->bottom(); |
| HeapWord* scan_limit = space->scan_limit(); |
| |
| while (cur_obj < scan_limit) { |
| assert(!space->scanned_block_is_obj(cur_obj) || |
| oop(cur_obj)->mark()->is_marked() || oop(cur_obj)->mark()->is_unlocked() || |
| oop(cur_obj)->mark()->has_bias_pattern(), |
| "these are the only valid states during a mark sweep"); |
| if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) { |
| // prefetch beyond cur_obj |
| Prefetch::write(cur_obj, interval); |
| size_t size = space->scanned_block_size(cur_obj); |
| compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top); |
| cur_obj += size; |
| end_of_live = cur_obj; |
| } else { |
| // run over all the contiguous dead objects |
| HeapWord* end = cur_obj; |
| do { |
| // prefetch beyond end |
| Prefetch::write(end, interval); |
| end += space->scanned_block_size(end); |
| } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked())); |
| |
| // see if we might want to pretend this object is alive so that |
| // we don't have to compact quite as often. |
| if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) { |
| oop obj = oop(cur_obj); |
| compact_top = cp->space->forward(obj, obj->size(), cp, compact_top); |
| end_of_live = end; |
| } else { |
| // otherwise, it really is a free region. |
| |
| // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object. |
| *(HeapWord**)cur_obj = end; |
| |
| // see if this is the first dead region. |
| if (first_dead == NULL) { |
| first_dead = cur_obj; |
| } |
| } |
| |
| // move on to the next object |
| cur_obj = end; |
| } |
| } |
| |
| assert(cur_obj == scan_limit, "just checking"); |
| space->_end_of_live = end_of_live; |
| if (first_dead != NULL) { |
| space->_first_dead = first_dead; |
| } else { |
| space->_first_dead = end_of_live; |
| } |
| |
| // save the compaction_top of the compaction space. |
| cp->space->set_compaction_top(compact_top); |
| } |
| |
| template <class SpaceType> |
| inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) { |
| // adjust all the interior pointers to point at the new locations of objects |
| // Used by MarkSweep::mark_sweep_phase3() |
| |
| HeapWord* cur_obj = space->bottom(); |
| HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward". |
| HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward". |
| |
| assert(first_dead <= end_of_live, "Stands to reason, no?"); |
| |
| const intx interval = PrefetchScanIntervalInBytes; |
| |
| debug_only(HeapWord* prev_obj = NULL); |
| while (cur_obj < end_of_live) { |
| Prefetch::write(cur_obj, interval); |
| if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) { |
| // cur_obj is alive |
| // point all the oops to the new location |
| size_t size = MarkSweep::adjust_pointers(oop(cur_obj)); |
| size = space->adjust_obj_size(size); |
| debug_only(prev_obj = cur_obj); |
| cur_obj += size; |
| } else { |
| debug_only(prev_obj = cur_obj); |
| // cur_obj is not a live object, instead it points at the next live object |
| cur_obj = *(HeapWord**)cur_obj; |
| assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj)); |
| } |
| } |
| |
| assert(cur_obj == end_of_live, "just checking"); |
| } |
| |
| #ifdef ASSERT |
| template <class SpaceType> |
| inline void CompactibleSpace::verify_up_to_first_dead(SpaceType* space) { |
| HeapWord* cur_obj = space->bottom(); |
| |
| if (cur_obj < space->_end_of_live && space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) { |
| // we have a chunk of the space which hasn't moved and we've reinitialized |
| // the mark word during the previous pass, so we can't use is_gc_marked for |
| // the traversal. |
| HeapWord* prev_obj = NULL; |
| |
| while (cur_obj < space->_first_dead) { |
| size_t size = space->obj_size(cur_obj); |
| assert(!oop(cur_obj)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); |
| prev_obj = cur_obj; |
| cur_obj += size; |
| } |
| } |
| } |
| #endif |
| |
| template <class SpaceType> |
| inline void CompactibleSpace::clear_empty_region(SpaceType* space) { |
| // Let's remember if we were empty before we did the compaction. |
| bool was_empty = space->used_region().is_empty(); |
| // Reset space after compaction is complete |
| space->reset_after_compaction(); |
| // We do this clear, below, since it has overloaded meanings for some |
| // space subtypes. For example, OffsetTableContigSpace's that were |
| // compacted into will have had their offset table thresholds updated |
| // continuously, but those that weren't need to have their thresholds |
| // re-initialized. Also mangles unused area for debugging. |
| if (space->used_region().is_empty()) { |
| if (!was_empty) space->clear(SpaceDecorator::Mangle); |
| } else { |
| if (ZapUnusedHeapArea) space->mangle_unused_area(); |
| } |
| } |
| |
| template <class SpaceType> |
| inline void CompactibleSpace::scan_and_compact(SpaceType* space) { |
| // Copy all live objects to their new location |
| // Used by MarkSweep::mark_sweep_phase4() |
| |
| verify_up_to_first_dead(space); |
| |
| HeapWord* const bottom = space->bottom(); |
| HeapWord* const end_of_live = space->_end_of_live; |
| |
| assert(space->_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(space->_first_dead), p2i(end_of_live)); |
| if (space->_first_dead == end_of_live && (bottom == end_of_live || !oop(bottom)->is_gc_marked())) { |
| // Nothing to compact. The space is either empty or all live object should be left in place. |
| clear_empty_region(space); |
| return; |
| } |
| |
| const intx scan_interval = PrefetchScanIntervalInBytes; |
| const intx copy_interval = PrefetchCopyIntervalInBytes; |
| |
| assert(bottom < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(bottom), p2i(end_of_live)); |
| HeapWord* cur_obj = bottom; |
| if (space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) { |
| // All object before _first_dead can be skipped. They should not be moved. |
| // A pointer to the first live object is stored at the memory location for _first_dead. |
| cur_obj = *(HeapWord**)(space->_first_dead); |
| } |
| |
| debug_only(HeapWord* prev_obj = NULL); |
| while (cur_obj < end_of_live) { |
| if (!oop(cur_obj)->is_gc_marked()) { |
| debug_only(prev_obj = cur_obj); |
| // The first word of the dead object contains a pointer to the next live object or end of space. |
| cur_obj = *(HeapWord**)cur_obj; |
| assert(cur_obj > prev_obj, "we should be moving forward through memory"); |
| } else { |
| // prefetch beyond q |
| Prefetch::read(cur_obj, scan_interval); |
| |
| // size and destination |
| size_t size = space->obj_size(cur_obj); |
| HeapWord* compaction_top = (HeapWord*)oop(cur_obj)->forwardee(); |
| |
| // prefetch beyond compaction_top |
| Prefetch::write(compaction_top, copy_interval); |
| |
| // copy object and reinit its mark |
| assert(cur_obj != compaction_top, "everything in this pass should be moving"); |
| Copy::aligned_conjoint_words(cur_obj, compaction_top, size); |
| oop(compaction_top)->init_mark(); |
| assert(oop(compaction_top)->klass() != NULL, "should have a class"); |
| |
| debug_only(prev_obj = cur_obj); |
| cur_obj += size; |
| } |
| } |
| |
| clear_empty_region(space); |
| } |
| |
| size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const { |
| return oop(addr)->size(); |
| } |
| |
| #endif // SHARE_VM_GC_SHARED_SPACE_INLINE_HPP |