Revert of [Tracing] Use TracingCategoryObserver in gc statistics (patchset #5...

Revert of [Tracing] Use TracingCategoryObserver in gc statistics (patchset #5 id:100001 of https://codereview.chromium.org/2459903003/ )

Reason for revert:
Speculative revert for blocking roll:
https://codereview.chromium.org/2473003006/

E.g.:
https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_rel_ng/builds/331898

Original issue's description:
> [Tracing] Use TracingCategoryObserver in gc statistics
>
> This patch is a follow-up patch to enable gc statistics to use
> TracingCategoryObserver.
>
> Previously we need to pass --track_gc_object_stats to v8 if we want to enable
> gc statistics in tracing. In this patch, we introducce an integer flag
> FLAG_gc_stats, and FLAG_track_gc_object_stats and FLAG_trace_gc_object_stats
> will set it to 0x01, tracing will set it to 0x10 when we start tracing and
> reset the bit when we stop tracing.
>
> BUG=v8:5590

TBR=fmeawad@chromium.org,mlippautz@chromium.org,lpy@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5590

Review-Url: https://codereview.chromium.org/2477143002
Cr-Commit-Position: refs/heads/master@{#40785}

src/api.cc

@@ -8087,7 +8087,7 @@ size_t Isolate::NumberOfTrackedHeapObjectTypes() {
 bool Isolate::GetHeapObjectStatisticsAtLastGC(
     HeapObjectStatistics* object_statistics, size_t type_index) {
   if (!object_statistics) return false;
-  if (V8_LIKELY(!i::FLAG_gc_stats)) return false;
+  if (!i::FLAG_track_gc_object_stats) return false;
 
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   i::Heap* heap = isolate->heap();

src/bootstrapper.cc

@@ -4016,7 +4016,7 @@ bool Genesis::InstallExtensions(Handle<Context> native_context,
           InstallExtension(isolate, "v8/gc", &extension_states)) &&
          (!FLAG_expose_externalize_string ||
           InstallExtension(isolate, "v8/externalize", &extension_states)) &&
-         (!FLAG_gc_stats ||
+         (!FLAG_track_gc_object_stats ||
           InstallExtension(isolate, "v8/statistics", &extension_states)) &&
          (!FLAG_expose_trigger_failure ||
           InstallExtension(isolate, "v8/trigger-failure", &extension_states)) &&

src/d8.cc

@@ -2864,7 +2864,7 @@ int Shell::Main(int argc, char* argv[]) {
       base::SysInfo::AmountOfVirtualMemory());
 
   Shell::counter_map_ = new CounterMap();
-  if (i::FLAG_dump_counters || i::FLAG_gc_stats) {
+  if (i::FLAG_dump_counters || i::FLAG_track_gc_object_stats) {
     create_params.counter_lookup_callback = LookupCounter;
     create_params.create_histogram_callback = CreateHistogram;
     create_params.add_histogram_sample_callback = AddHistogramSample;

src/flag-definitions.h

@@ -741,10 +741,7 @@ DEFINE_BOOL(track_gc_object_stats, false,
             "track object counts and memory usage")
 DEFINE_BOOL(trace_gc_object_stats, false,
             "trace object counts and memory usage")
-DEFINE_INT(gc_stats, 0, "Used by tracing internally to enable gc statistics")
 DEFINE_IMPLICATION(trace_gc_object_stats, track_gc_object_stats)
-DEFINE_VALUE_IMPLICATION(track_gc_object_stats, gc_stats, 1)
-DEFINE_VALUE_IMPLICATION(trace_gc_object_stats, gc_stats, 1)
 DEFINE_NEG_IMPLICATION(trace_gc_object_stats, incremental_marking)
 DEFINE_BOOL(track_detached_contexts, true,
             "track native contexts that are expected to be garbage collected")

src/heap/heap-inl.h

@@ -12,7 +12,6 @@
 #include "src/heap/heap.h"
 #include "src/heap/incremental-marking-inl.h"
 #include "src/heap/mark-compact.h"
-#include "src/heap/object-stats.h"
 #include "src/heap/remembered-set.h"
 #include "src/heap/spaces-inl.h"
 #include "src/heap/store-buffer.h"
@@ -810,16 +809,6 @@ void Heap::SetSerializedTemplates(FixedArray* templates) {
   set_serialized_templates(templates);
 }
 
-void Heap::CreateObjectStats() {
-  if (V8_LIKELY(FLAG_gc_stats == 0)) return;
-  if (!live_object_stats_) {
-    live_object_stats_ = new ObjectStats(this);
-  }
-  if (!dead_object_stats_) {
-    dead_object_stats_ = new ObjectStats(this);
-  }
-}
-
 AlwaysAllocateScope::AlwaysAllocateScope(Isolate* isolate)
     : heap_(isolate->heap()) {
   heap_->always_allocate_scope_count_.Increment(1);

src/heap/heap.cc

@@ -5470,7 +5470,7 @@ bool Heap::SetUp() {
   mark_compact_collector_ = new MarkCompactCollector(this);
   gc_idle_time_handler_ = new GCIdleTimeHandler();
   memory_reducer_ = new MemoryReducer(this);
-  if (V8_UNLIKELY(FLAG_gc_stats)) {
+  if (FLAG_track_gc_object_stats) {
     live_object_stats_ = new ObjectStats(this);
     dead_object_stats_ = new ObjectStats(this);
   }

src/heap/heap.h

@@ -944,9 +944,6 @@ class Heap {
   // Returns whether it succeeded.
   bool CreateHeapObjects();
 
-  // Create ObjectStats if live_object_stats_ or dead_object_stats_ are nullptr.
-  V8_INLINE void CreateObjectStats();
-
   // Destroys all memory allocated by the heap.
   void TearDown();
 

src/heap/mark-compact.cc

@@ -25,7 +25,6 @@
 #include "src/heap/spaces-inl.h"
 #include "src/ic/ic.h"
 #include "src/ic/stub-cache.h"
-#include "src/tracing/tracing-category-observer.h"
 #include "src/utils-inl.h"
 #include "src/v8.h"
 
@@ -2237,21 +2236,17 @@ void MarkCompactCollector::VisitAllObjects(HeapObjectVisitor* visitor) {
 }
 
 void MarkCompactCollector::RecordObjectStats() {
-  if (V8_UNLIKELY(FLAG_gc_stats)) {
-    heap()->CreateObjectStats();
+  if (FLAG_track_gc_object_stats) {
     ObjectStatsVisitor visitor(heap(), heap()->live_object_stats_,
                                heap()->dead_object_stats_);
     VisitAllObjects(&visitor);
-    if (V8_UNLIKELY(FLAG_gc_stats &
-                    v8::tracing::TracingCategoryObserver::ENABLED_BY_TRACING)) {
-      std::stringstream live, dead;
-      heap()->live_object_stats_->Dump(live);
-      heap()->dead_object_stats_->Dump(dead);
-      TRACE_EVENT_INSTANT2(TRACE_DISABLED_BY_DEFAULT("v8.gc_stats"),
-                           "V8.GC_Objects_Stats", TRACE_EVENT_SCOPE_THREAD,
-                           "live", TRACE_STR_COPY(live.str().c_str()), "dead",
-                           TRACE_STR_COPY(dead.str().c_str()));
-    }
+    std::stringstream live, dead;
+    heap()->live_object_stats_->Dump(live);
+    heap()->dead_object_stats_->Dump(dead);
+    TRACE_EVENT_INSTANT2(TRACE_DISABLED_BY_DEFAULT("v8.gc_stats"),
+                         "V8.GC_Objects_Stats", TRACE_EVENT_SCOPE_THREAD,
+                         "live", TRACE_STR_COPY(live.str().c_str()), "dead",
+                         TRACE_STR_COPY(dead.str().c_str()));
     if (FLAG_trace_gc_object_stats) {
       heap()->live_object_stats_->PrintJSON("live");
       heap()->dead_object_stats_->PrintJSON("dead");

src/tracing/tracing-category-observer.cc

@@ -18,7 +18,6 @@ void TracingCategoryObserver::SetUp() {
   v8::internal::V8::GetCurrentPlatform()->AddTraceStateObserver(
       TracingCategoryObserver::instance_);
   TRACE_EVENT_WARMUP_CATEGORY(TRACE_DISABLED_BY_DEFAULT("v8.runtime_stats"));
-  TRACE_EVENT_WARMUP_CATEGORY(TRACE_DISABLED_BY_DEFAULT("v8.gc_stats"));
 }
 
 void TracingCategoryObserver::TearDown() {
@@ -34,16 +33,10 @@ void TracingCategoryObserver::OnTraceEnabled() {
   if (enabled) {
     v8::internal::FLAG_runtime_stats |= ENABLED_BY_TRACING;
   }
-  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("v8.gc_stats"),
-                                     &enabled);
-  if (enabled) {
-    v8::internal::FLAG_gc_stats |= ENABLED_BY_TRACING;
-  }
 }
 
 void TracingCategoryObserver::OnTraceDisabled() {
   v8::internal::FLAG_runtime_stats &= ~ENABLED_BY_TRACING;
-  v8::internal::FLAG_gc_stats &= ~ENABLED_BY_TRACING;
 }
 
 }  // namespace tracing