Java堆

• Image Space: 存放一些预加载的类
• Zygote Space: 对应Davlik的Zygote堆
• Allocation Space: 对应Dalvik的Active堆
• Large Object Space: 用来分配一些大对象

GC的类型

• kGcCauseForAlloc: 内存不够的情况下引起的GC
• kGcCauseBackground: 内存达到一定的阀值的时候引发的GC
• kGcCauseExplicit: System.gc显示调用的GC

// heap.cc: CollectGarbageInternal
collector::GcType Heap::CollectGarbageInternal(collector::GcType gc_type,
                                               GcCause gc_cause,
                                               bool clear_soft_references) {
  collector->Run(gc_cause, clear_soft_references || runtime->IsZygote());
  RequestTrim(self);
  // Grow the heap so that we know when to perform the next GC.
  GrowForUtilization(collector, bytes_allocated_before_gc);
  Dbg::GcDidFinish();
  return gc_type;
}

Foreground GC和Background GC切换

// ActivityThread.scheduleLaunchActivity
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident) {
            updateProcessState(procState, false);

            sendMessage(H.LAUNCH_ACTIVITY, r);
        }

// heap.cc: UpdateProcessState
void Heap::UpdateProcessState(ProcessState old_process_state, ProcessState new_process_state) {
  if (old_process_state != new_process_state) {
    const bool jank_perceptible = new_process_state == kProcessStateJankPerceptible;
    if (jank_perceptible) {
      RequestCollectorTransition(foreground_collector_type_, 0);
    } else {
      RequestCollectorTransition(background_collector_type_,
                                 kIsDebugBuild ? 0 : kCollectorTransitionWait);
    }
  }
}

相关资料

• Android GC 原理探究
• 老罗讲ART GC