| /* |
| * Copyright (c) 2001, 2015, 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. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "classfile/systemDictionary.hpp" |
| #include "gc/parallel/objectStartArray.hpp" |
| #include "gc/parallel/parallelScavengeHeap.hpp" |
| #include "gc/parallel/psMarkSweep.hpp" |
| #include "gc/parallel/psMarkSweepDecorator.hpp" |
| #include "gc/serial/markSweep.inline.hpp" |
| #include "gc/shared/spaceDecorator.hpp" |
| #include "oops/oop.inline.hpp" |
| #include "runtime/prefetch.inline.hpp" |
| |
| PSMarkSweepDecorator* PSMarkSweepDecorator::_destination_decorator = NULL; |
| |
| |
| void PSMarkSweepDecorator::set_destination_decorator_tenured() { |
| ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); |
| _destination_decorator = heap->old_gen()->object_mark_sweep(); |
| } |
| |
| void PSMarkSweepDecorator::advance_destination_decorator() { |
| ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); |
| |
| assert(_destination_decorator != NULL, "Sanity"); |
| |
| PSMarkSweepDecorator* first = heap->old_gen()->object_mark_sweep(); |
| PSMarkSweepDecorator* second = heap->young_gen()->eden_mark_sweep(); |
| PSMarkSweepDecorator* third = heap->young_gen()->from_mark_sweep(); |
| PSMarkSweepDecorator* fourth = heap->young_gen()->to_mark_sweep(); |
| |
| if ( _destination_decorator == first ) { |
| _destination_decorator = second; |
| } else if ( _destination_decorator == second ) { |
| _destination_decorator = third; |
| } else if ( _destination_decorator == third ) { |
| _destination_decorator = fourth; |
| } else { |
| fatal("PSMarkSweep attempting to advance past last compaction area"); |
| } |
| } |
| |
| PSMarkSweepDecorator* PSMarkSweepDecorator::destination_decorator() { |
| assert(_destination_decorator != NULL, "Sanity"); |
| |
| return _destination_decorator; |
| } |
| |
| // FIX ME FIX ME FIX ME FIX ME!!!!!!!!! |
| // The object forwarding code is duplicated. Factor this out!!!!! |
| // |
| // This method "precompacts" objects inside its space to dest. It places forwarding |
| // pointers into markOops for use by adjust_pointers. If "dest" should overflow, we |
| // finish by compacting into our own space. |
| |
| void PSMarkSweepDecorator::precompact() { |
| // Reset our own compact top. |
| set_compaction_top(space()->bottom()); |
| |
| /* 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. This is a significant |
| * performance improvement! |
| */ |
| bool skip_dead = ((PSMarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0); |
| |
| size_t allowed_deadspace = 0; |
| if (skip_dead) { |
| const size_t ratio = allowed_dead_ratio(); |
| allowed_deadspace = space()->capacity_in_words() * ratio / 100; |
| } |
| |
| // Fetch the current destination decorator |
| PSMarkSweepDecorator* dest = destination_decorator(); |
| ObjectStartArray* start_array = dest->start_array(); |
| |
| HeapWord* compact_top = dest->compaction_top(); |
| HeapWord* compact_end = dest->space()->end(); |
| |
| HeapWord* q = space()->bottom(); |
| HeapWord* t = space()->top(); |
| |
| HeapWord* end_of_live= q; /* One byte beyond the last byte of the last |
| live object. */ |
| HeapWord* first_dead = space()->end(); /* The first dead object. */ |
| |
| const intx interval = PrefetchScanIntervalInBytes; |
| |
| while (q < t) { |
| assert(oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || |
| oop(q)->mark()->has_bias_pattern(), |
| "these are the only valid states during a mark sweep"); |
| if (oop(q)->is_gc_marked()) { |
| /* prefetch beyond q */ |
| Prefetch::write(q, interval); |
| size_t size = oop(q)->size(); |
| |
| size_t compaction_max_size = pointer_delta(compact_end, compact_top); |
| |
| // This should only happen if a space in the young gen overflows the |
| // old gen. If that should happen, we null out the start_array, because |
| // the young spaces are not covered by one. |
| while(size > compaction_max_size) { |
| // First record the last compact_top |
| dest->set_compaction_top(compact_top); |
| |
| // Advance to the next compaction decorator |
| advance_destination_decorator(); |
| dest = destination_decorator(); |
| |
| // Update compaction info |
| start_array = dest->start_array(); |
| compact_top = dest->compaction_top(); |
| compact_end = dest->space()->end(); |
| assert(compact_top == dest->space()->bottom(), "Advanced to space already in use"); |
| assert(compact_end > compact_top, "Must always be space remaining"); |
| compaction_max_size = |
| pointer_delta(compact_end, compact_top); |
| } |
| |
| // store the forwarding pointer into the mark word |
| if (q != compact_top) { |
| oop(q)->forward_to(oop(compact_top)); |
| assert(oop(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. |
| oop(q)->init_mark(); |
| assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL"); |
| } |
| |
| // Update object start array |
| if (start_array) { |
| start_array->allocate_block(compact_top); |
| } |
| |
| compact_top += size; |
| assert(compact_top <= dest->space()->end(), |
| "Exceeding space in destination"); |
| |
| q += size; |
| end_of_live = q; |
| } else { |
| /* run over all the contiguous dead objects */ |
| HeapWord* end = q; |
| do { |
| /* prefetch beyond end */ |
| Prefetch::write(end, interval); |
| end += oop(end)->size(); |
| } while (end < t && (!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 (allowed_deadspace > 0 && q == compact_top) { |
| size_t sz = pointer_delta(end, q); |
| if (insert_deadspace(allowed_deadspace, q, sz)) { |
| size_t compaction_max_size = pointer_delta(compact_end, compact_top); |
| |
| // This should only happen if a space in the young gen overflows the |
| // old gen. If that should happen, we null out the start_array, because |
| // the young spaces are not covered by one. |
| while (sz > compaction_max_size) { |
| // First record the last compact_top |
| dest->set_compaction_top(compact_top); |
| |
| // Advance to the next compaction decorator |
| advance_destination_decorator(); |
| dest = destination_decorator(); |
| |
| // Update compaction info |
| start_array = dest->start_array(); |
| compact_top = dest->compaction_top(); |
| compact_end = dest->space()->end(); |
| assert(compact_top == dest->space()->bottom(), "Advanced to space already in use"); |
| assert(compact_end > compact_top, "Must always be space remaining"); |
| compaction_max_size = |
| pointer_delta(compact_end, compact_top); |
| } |
| |
| // store the forwarding pointer into the mark word |
| if (q != compact_top) { |
| oop(q)->forward_to(oop(compact_top)); |
| assert(oop(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. |
| oop(q)->init_mark(); |
| assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL"); |
| } |
| |
| // Update object start array |
| if (start_array) { |
| start_array->allocate_block(compact_top); |
| } |
| |
| compact_top += sz; |
| assert(compact_top <= dest->space()->end(), |
| "Exceeding space in destination"); |
| |
| q = end; |
| end_of_live = end; |
| continue; |
| } |
| } |
| |
| // q is a pointer to a dead object. Use this dead memory to store a pointer to the next live object. |
| (*(HeapWord**)q) = end; |
| |
| /* see if this is the first dead region. */ |
| if (q < first_dead) { |
| first_dead = q; |
| } |
| |
| /* move on to the next object */ |
| q = end; |
| } |
| } |
| |
| assert(q == t, "just checking"); |
| _end_of_live = end_of_live; |
| if (end_of_live < first_dead) { |
| first_dead = end_of_live; |
| } |
| _first_dead = first_dead; |
| |
| // Update compaction top |
| dest->set_compaction_top(compact_top); |
| } |
| |
| bool PSMarkSweepDecorator::insert_deadspace(size_t& allowed_deadspace_words, |
| HeapWord* q, size_t deadlength) { |
| if (allowed_deadspace_words >= deadlength) { |
| allowed_deadspace_words -= deadlength; |
| CollectedHeap::fill_with_object(q, deadlength); |
| oop(q)->set_mark(oop(q)->mark()->set_marked()); |
| assert((int) deadlength == oop(q)->size(), "bad filler object size"); |
| // Recall that we required "q == compaction_top". |
| return true; |
| } else { |
| allowed_deadspace_words = 0; |
| return false; |
| } |
| } |
| |
| void PSMarkSweepDecorator::adjust_pointers() { |
| // adjust all the interior pointers to point at the new locations of objects |
| // Used by MarkSweep::mark_sweep_phase3() |
| |
| HeapWord* q = space()->bottom(); |
| HeapWord* t = _end_of_live; // Established by "prepare_for_compaction". |
| |
| assert(_first_dead <= _end_of_live, "Stands to reason, no?"); |
| |
| if (q < t && _first_dead > q && |
| !oop(q)->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* end = _first_dead; |
| |
| while (q < end) { |
| // point all the oops to the new location |
| size_t size = MarkSweep::adjust_pointers(oop(q)); |
| q += size; |
| } |
| |
| if (_first_dead == t) { |
| q = t; |
| } else { |
| // The first dead object should contain a pointer to the first live object |
| q = *(HeapWord**)_first_dead; |
| } |
| } |
| const intx interval = PrefetchScanIntervalInBytes; |
| |
| debug_only(HeapWord* prev_q = NULL); |
| while (q < t) { |
| // prefetch beyond q |
| Prefetch::write(q, interval); |
| if (oop(q)->is_gc_marked()) { |
| // q is alive |
| // point all the oops to the new location |
| size_t size = MarkSweep::adjust_pointers(oop(q)); |
| debug_only(prev_q = q); |
| q += size; |
| } else { |
| debug_only(prev_q = q); |
| // The first dead object is no longer an object. At that memory address, |
| // there is a pointer to the first live object that the previous phase found. |
| q = *(HeapWord**)q; |
| assert(q > prev_q, "we should be moving forward through memory, q: " PTR_FORMAT ", prev_q: " PTR_FORMAT, p2i(q), p2i(prev_q)); |
| } |
| } |
| |
| assert(q == t, "just checking"); |
| } |
| |
| void PSMarkSweepDecorator::compact(bool mangle_free_space ) { |
| // Copy all live objects to their new location |
| // Used by MarkSweep::mark_sweep_phase4() |
| |
| HeapWord* q = space()->bottom(); |
| HeapWord* const t = _end_of_live; |
| debug_only(HeapWord* prev_q = NULL); |
| |
| if (q < t && _first_dead > q && |
| !oop(q)->is_gc_marked()) { |
| #ifdef ASSERT |
| // 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* const end = _first_dead; |
| |
| while (q < end) { |
| size_t size = oop(q)->size(); |
| assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); |
| debug_only(prev_q = q); |
| q += size; |
| } |
| #endif |
| |
| if (_first_dead == t) { |
| q = t; |
| } else { |
| // $$$ Funky |
| q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); |
| } |
| } |
| |
| const intx scan_interval = PrefetchScanIntervalInBytes; |
| const intx copy_interval = PrefetchCopyIntervalInBytes; |
| |
| while (q < t) { |
| if (!oop(q)->is_gc_marked()) { |
| // mark is pointer to next marked oop |
| debug_only(prev_q = q); |
| q = (HeapWord*) oop(q)->mark()->decode_pointer(); |
| assert(q > prev_q, "we should be moving forward through memory"); |
| } else { |
| // prefetch beyond q |
| Prefetch::read(q, scan_interval); |
| |
| // size and destination |
| size_t size = oop(q)->size(); |
| HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); |
| |
| // prefetch beyond compaction_top |
| Prefetch::write(compaction_top, copy_interval); |
| |
| // copy object and reinit its mark |
| assert(q != compaction_top, "everything in this pass should be moving"); |
| Copy::aligned_conjoint_words(q, compaction_top, size); |
| oop(compaction_top)->init_mark(); |
| assert(oop(compaction_top)->klass() != NULL, "should have a class"); |
| |
| debug_only(prev_q = q); |
| q += size; |
| } |
| } |
| |
| assert(compaction_top() >= space()->bottom() && compaction_top() <= space()->end(), |
| "should point inside space"); |
| space()->set_top(compaction_top()); |
| |
| if (mangle_free_space) { |
| space()->mangle_unused_area(); |
| } |
| } |