[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 81605209e52e373ec6d972d44b5b8c842c8b6b65..6cdc6ef670166a53b982fca75ca42348c49fea50 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -1737,11 +1737,111 @@ void RenderThreadImpl::OnProcessPurgeAndSuspend() {
   ChildThreadImpl::OnProcessPurgeAndSuspend();
   if (is_renderer_suspended_)
     return;
+
+  blink_memory_stats_ = blink::WebMemoryStatistics::Get();
+  malloc_stats_ = base::memory::MallocStatistics::GetStatistics();
+  discardable_stats_ =
+      ChildThreadImpl::discardable_shared_memory_manager()->GetStatistics();
+  if (v8::Isolate* isolate = blink::mainThreadIsolate()) {
+    v8::HeapStatistics v8_heap_statistics;
+    isolate->GetHeapStatistics(&v8_heap_statistics);
+    v8_total_heap_usage_ = v8_heap_statistics.total_heap_size();
+  } else {
+    v8_total_heap_usage_ = 0;
+  }
+
+  // TODO(tasak): use MemoryCoordinator instead of NotifyMemoryPressure.
+  base::MemoryPressureListener::NotifyMemoryPressure(
+      base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL);
+  base::allocator::ReleaseFreeMemory();
+
+  // Since purging is not a synchronouse task (e.g. v8 GC, oilpan GC, ...),
+  // we need to wait until the task is finished. So wait 5 seconds and
+  // update purge+suspend uma histogram.
+  GetRendererScheduler()->DefaultTaskRunner()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&RenderThreadImpl::OnDumpMemoryUsage, base::Unretained(this)),
+      base::TimeDelta::FromSeconds(5));

[Primiano Tucci (use gerrit), 2016/09/23 09:24:34]

This smells odd. I understand purging is not sync. Doesn't it provide a "Done"
async callback though?

[tasak, 2016/09/23 10:12:18]

I agree with you. When we have MemoryCoordinatorV0, I will add "Done" callback.

Talking about current MemoryPressureListener... I have a patch which modifies
observer_list_threadsafe.h to add "NotifyAndReply" method.
However, I think, the patch is too much...

[Primiano Tucci (use gerrit), 2016/09/23 19:31:09]

Ok I see. ack. maybe add a comment here.

+
   // TODO(hajimehoshi): Implement purging e.g. cache (crbug/607077)
   is_renderer_suspended_ = true;
   renderer_scheduler_->SuspendRenderer();
 }
 
+// For purge+suspend, report memory usage diff by using UMA_HISTOGRAM.
+void RenderThreadImpl::OnDumpMemoryUsage() {
+  // If this renderer is resumed, we should not update uma.
+  if (!is_renderer_suspended_)
+    return;
+
+  blink::WebMemoryStatistics current_blink_memory_stats =
+      blink::WebMemoryStatistics::Get();
+
+  base::memory::MallocStatistics current_malloc_stats =
+      base::memory::MallocStatistics::GetStatistics();
+
+  ChildDiscardableSharedMemoryManager::Statistics current_discardable_stats =
+      ChildThreadImpl::discardable_shared_memory_manager()->GetStatistics();
+
+  size_t v8_total_heap_usage = 0;
+  if (v8::Isolate* isolate = blink::mainThreadIsolate()) {
+    v8::HeapStatistics v8_heap_statistics;
+    isolate->GetHeapStatistics(&v8_heap_statistics);
+    v8_total_heap_usage = v8_heap_statistics.total_heap_size();
+  }
+
+  int64_t diff = blink_memory_stats_.partitionAllocTotalAllocatedBytes -
+                 current_blink_memory_stats.partitionAllocTotalAllocatedBytes;
+  int64_t total_diff = diff;
+  if (diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.PartitionAllocShrink", diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.PartitionAllocGrowth", -diff);
+
+  diff = blink_memory_stats_.blinkGCTotalAllocatedBytes -
+         current_blink_memory_stats.blinkGCTotalAllocatedBytes;
+  if (diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.BlinkGCShrink", diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.BlinkGCGrowth", -diff);
+  total_diff += diff;
+
+  diff = malloc_stats_.allocated_objects_size -
+         current_malloc_stats.allocated_objects_size;
+  if (diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.MallocShrink", diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.MallocGrowth", -diff);
+  total_diff += diff;
+
+  diff = (discardable_stats_.total_size - discardable_stats_.freelist_size) -
+         (current_discardable_stats.total_size -
+          current_discardable_stats.freelist_size);
+  if (diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.DiscardableShrink", diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.DiscardableGrowth", -diff);
+  total_diff += diff;
+
+  diff = v8_total_heap_usage_ - v8_total_heap_usage;
+  if (diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.V8HeapShrink", diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.V8HeapGrowth", -diff);
+  total_diff += diff;
+
+  if (total_diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.TotalShrink", total_diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.TotalGrowth", -total_diff);
+
+  diff = malloc_stats_.resident_size - current_malloc_stats.resident_size;
+  if (diff > 0)
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.ResidentSizeShrink", diff);
+  else
+    UMA_HISTOGRAM_MEMORY_KB("PurgeAndSuspend.ResidentSizeGrowth", -diff);
+}
+
 void RenderThreadImpl::OnCreateNewFrame(FrameMsg_NewFrame_Params params) {
   // Debug cases of https://crbug.com/626802.
   base::debug::SetCrashKeyValue("newframe_routing_id",