garbage_collector.cc revision 1f3b5358b28a83f0929bdd8ce738f06908677fb7 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#define ATRACE_TAG ATRACE_TAG_DALVIK
18
19#include <stdio.h>
20#include <cutils/trace.h>
21
22#include "garbage_collector.h"
23
24#include "base/histogram-inl.h"
25#include "base/logging.h"
26#include "base/mutex-inl.h"
27#include "gc/accounting/heap_bitmap.h"
28#include "gc/space/large_object_space.h"
29#include "gc/space/space-inl.h"
30#include "thread-inl.h"
31#include "thread_list.h"
32
33namespace art {
34namespace gc {
35namespace collector {
36
37GarbageCollector::GarbageCollector(Heap* heap, const std::string& name)
38    : heap_(heap),
39      name_(name),
40      gc_cause_(kGcCauseForAlloc),
41      clear_soft_references_(false),
42      verbose_(VLOG_IS_ON(heap)),
43      duration_ns_(0),
44      timings_(name_.c_str(), true, verbose_),
45      pause_histogram_((name_ + " paused").c_str(), kPauseBucketSize, kPauseBucketCount),
46      cumulative_timings_(name) {
47  ResetCumulativeStatistics();
48}
49
50bool GarbageCollector::HandleDirtyObjectsPhase() {
51  DCHECK(IsConcurrent());
52  return true;
53}
54
55void GarbageCollector::RegisterPause(uint64_t nano_length) {
56  pause_times_.push_back(nano_length);
57}
58
59void GarbageCollector::ResetCumulativeStatistics() {
60  cumulative_timings_.Reset();
61  pause_histogram_.Reset();
62  total_time_ns_ = 0;
63  total_freed_objects_ = 0;
64  total_freed_bytes_ = 0;
65}
66
67void GarbageCollector::Run(GcCause gc_cause, bool clear_soft_references) {
68  ThreadList* thread_list = Runtime::Current()->GetThreadList();
69  Thread* self = Thread::Current();
70  uint64_t start_time = NanoTime();
71  pause_times_.clear();
72  duration_ns_ = 0;
73  clear_soft_references_ = clear_soft_references;
74  gc_cause_ = gc_cause;
75
76  // Reset stats.
77  freed_bytes_ = 0;
78  freed_large_object_bytes_ = 0;
79  freed_objects_ = 0;
80  freed_large_objects_ = 0;
81
82  InitializePhase();
83
84  if (!IsConcurrent()) {
85    // Pause is the entire length of the GC.
86    uint64_t pause_start = NanoTime();
87    ATRACE_BEGIN("Application threads suspended");
88    // Mutator lock may be already exclusively held when we do garbage collections for changing the
89    // current collector / allocator during process state updates.
90    if (Locks::mutator_lock_->IsExclusiveHeld(self)) {
91      GetHeap()->RevokeAllThreadLocalBuffers();
92      MarkingPhase();
93      ReclaimPhase();
94    } else {
95      thread_list->SuspendAll();
96      GetHeap()->RevokeAllThreadLocalBuffers();
97      MarkingPhase();
98      ReclaimPhase();
99      thread_list->ResumeAll();
100    }
101    ATRACE_END();
102    RegisterPause(NanoTime() - pause_start);
103  } else {
104    CHECK(!Locks::mutator_lock_->IsExclusiveHeld(self));
105    Thread* self = Thread::Current();
106    {
107      ReaderMutexLock mu(self, *Locks::mutator_lock_);
108      MarkingPhase();
109    }
110    bool done = false;
111    while (!done) {
112      uint64_t pause_start = NanoTime();
113      ATRACE_BEGIN("Suspending mutator threads");
114      thread_list->SuspendAll();
115      ATRACE_END();
116      ATRACE_BEGIN("All mutator threads suspended");
117      done = HandleDirtyObjectsPhase();
118      if (done) {
119        GetHeap()->RevokeAllThreadLocalBuffers();
120      }
121      ATRACE_END();
122      uint64_t pause_end = NanoTime();
123      ATRACE_BEGIN("Resuming mutator threads");
124      thread_list->ResumeAll();
125      ATRACE_END();
126      RegisterPause(pause_end - pause_start);
127    }
128    {
129      ReaderMutexLock mu(self, *Locks::mutator_lock_);
130      ReclaimPhase();
131    }
132  }
133  FinishPhase();
134  uint64_t end_time = NanoTime();
135  duration_ns_ = end_time - start_time;
136  total_time_ns_ += GetDurationNs();
137  for (uint64_t pause_time : pause_times_) {
138    pause_histogram_.AddValue(pause_time / 1000);
139  }
140}
141
142void GarbageCollector::SwapBitmaps() {
143  // Swap the live and mark bitmaps for each alloc space. This is needed since sweep re-swaps
144  // these bitmaps. The bitmap swapping is an optimization so that we do not need to clear the live
145  // bits of dead objects in the live bitmap.
146  const GcType gc_type = GetGcType();
147  for (const auto& space : GetHeap()->GetContinuousSpaces()) {
148    // We never allocate into zygote spaces.
149    if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyAlwaysCollect ||
150        (gc_type == kGcTypeFull &&
151         space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect)) {
152      accounting::SpaceBitmap* live_bitmap = space->GetLiveBitmap();
153      accounting::SpaceBitmap* mark_bitmap = space->GetMarkBitmap();
154      if (live_bitmap != nullptr && live_bitmap != mark_bitmap) {
155        heap_->GetLiveBitmap()->ReplaceBitmap(live_bitmap, mark_bitmap);
156        heap_->GetMarkBitmap()->ReplaceBitmap(mark_bitmap, live_bitmap);
157        CHECK(space->IsContinuousMemMapAllocSpace());
158        space->AsContinuousMemMapAllocSpace()->SwapBitmaps();
159      }
160    }
161  }
162  for (const auto& disc_space : GetHeap()->GetDiscontinuousSpaces()) {
163    space::LargeObjectSpace* space = down_cast<space::LargeObjectSpace*>(disc_space);
164    accounting::ObjectSet* live_set = space->GetLiveObjects();
165    accounting::ObjectSet* mark_set = space->GetMarkObjects();
166    heap_->GetLiveBitmap()->ReplaceObjectSet(live_set, mark_set);
167    heap_->GetMarkBitmap()->ReplaceObjectSet(mark_set, live_set);
168    down_cast<space::LargeObjectSpace*>(space)->SwapBitmaps();
169  }
170}
171
172}  // namespace collector
173}  // namespace gc
174}  // namespace art
175