[zone-stats] Introduce v8.zone_stats tracing category

... in order to make it possible to collect zone memory usage stats
from Chrome.

Drive-by-cleanup: move TracingFlags definition to a separate file.

Bug: v8:10572
Change-Id: I05fb65e207d573d5c18821067cfff4c37f2d77cd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2226561
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68135}

BUILD.gn

@@ -2630,6 +2630,8 @@ v8_source_set("v8_base_without_compiler") {
     "src/logging/log.cc",
     "src/logging/log.h",
     "src/logging/off-thread-logger.h",
+    "src/logging/tracing-flags.cc",
+    "src/logging/tracing-flags.h",
     "src/numbers/bignum-dtoa.cc",
     "src/numbers/bignum-dtoa.h",
     "src/numbers/bignum.cc",

src/api/api.cc

@@ -11,11 +11,10 @@
 #include <utility>  // For move
 #include <vector>
 
-#include "src/api/api-inl.h"
-
 #include "include/v8-fast-api-calls.h"
 #include "include/v8-profiler.h"
 #include "include/v8-util.h"
+#include "src/api/api-inl.h"
 #include "src/api/api-natives.h"
 #include "src/base/functional.h"
 #include "src/base/logging.h"
@@ -58,6 +57,7 @@
 #include "src/json/json-parser.h"
 #include "src/json/json-stringifier.h"
 #include "src/logging/counters.h"
+#include "src/logging/tracing-flags.h"
 #include "src/numbers/conversions-inl.h"
 #include "src/objects/api-callbacks.h"
 #include "src/objects/contexts.h"

src/flags/flag-definitions.h

@@ -965,6 +965,10 @@ DEFINE_BOOL(track_gc_object_stats, false,
 DEFINE_BOOL(trace_gc_object_stats, false,
             "trace object counts and memory usage")
 DEFINE_BOOL(trace_zone_stats, false, "trace zone memory usage")
+DEFINE_GENERIC_IMPLICATION(
+    trace_zone_stats,
+    TracingFlags::zone_stats.store(
+        v8::tracing::TracingCategoryObserver::ENABLED_BY_NATIVE))
 DEFINE_BOOL(track_retaining_path, false,
             "enable support for tracking retaining path")
 DEFINE_DEBUG_BOOL(trace_backing_store, false, "trace backing store events")

src/logging/counters-inl.h

@@ -6,6 +6,7 @@
 #define V8_LOGGING_COUNTERS_INL_H_
 
 #include "src/logging/counters.h"
+#include "src/logging/tracing-flags.h"
 
 namespace v8 {
 namespace internal {

src/logging/counters.cc

@@ -17,11 +17,6 @@
 namespace v8 {
 namespace internal {
 
-std::atomic_uint TracingFlags::runtime_stats{0};
-std::atomic_uint TracingFlags::gc{0};
-std::atomic_uint TracingFlags::gc_stats{0};
-std::atomic_uint TracingFlags::ic_stats{0};
-
 StatsTable::StatsTable(Counters* counters)
     : lookup_function_(nullptr),
       create_histogram_function_(nullptr),

src/logging/counters.h

@@ -16,6 +16,7 @@
 #include "src/execution/isolate.h"
 #include "src/init/heap-symbols.h"
 #include "src/logging/counters-definitions.h"
+#include "src/logging/tracing-flags.h"
 #include "src/objects/objects.h"
 #include "src/runtime/runtime.h"
 #include "src/tracing/trace-event.h"
@@ -26,33 +27,6 @@
 namespace v8 {
 namespace internal {
 
-// This struct contains a set of flags that can be modified from multiple
-// threads at runtime unlike the normal FLAG_-like flags which are not modified
-// after V8 instance is initialized.
-
-struct TracingFlags {
-  static V8_EXPORT_PRIVATE std::atomic_uint runtime_stats;
-  static V8_EXPORT_PRIVATE std::atomic_uint gc;
-  static V8_EXPORT_PRIVATE std::atomic_uint gc_stats;
-  static V8_EXPORT_PRIVATE std::atomic_uint ic_stats;
-
-  static bool is_runtime_stats_enabled() {
-    return runtime_stats.load(std::memory_order_relaxed) != 0;
-  }
-
-  static bool is_gc_enabled() {
-    return gc.load(std::memory_order_relaxed) != 0;
-  }
-
-  static bool is_gc_stats_enabled() {
-    return gc_stats.load(std::memory_order_relaxed) != 0;
-  }
-
-  static bool is_ic_stats_enabled() {
-    return ic_stats.load(std::memory_order_relaxed) != 0;
-  }
-};
-
 // StatsCounters is an interface for plugging into external
 // counters for monitoring.  Counters can be looked up and
 // manipulated by name.

src/logging/log-utils.h

@@ -37,7 +37,7 @@ class Log {
            FLAG_log_suspect || FLAG_ll_prof || FLAG_perf_basic_prof ||
            FLAG_perf_prof || FLAG_log_source_code || FLAG_gdbjit ||
            FLAG_log_internal_timer_events || FLAG_prof_cpp || FLAG_trace_ic ||
-           FLAG_log_function_events;
+           FLAG_log_function_events || FLAG_trace_zone_stats;
   }
 
   // Frees all resources acquired in Initialize and Open... functions.

src/logging/tracing-flags.cc

@@ -0,0 +1,17 @@
+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/logging/tracing-flags.h"
+
+namespace v8 {
+namespace internal {
+
+std::atomic_uint TracingFlags::runtime_stats{0};
+std::atomic_uint TracingFlags::gc{0};
+std::atomic_uint TracingFlags::gc_stats{0};
+std::atomic_uint TracingFlags::ic_stats{0};
+std::atomic_uint TracingFlags::zone_stats{0};
+
+}  // namespace internal
+}  // namespace v8

src/logging/tracing-flags.h

@@ -0,0 +1,50 @@
+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_LOGGING_TRACING_FLAGS_H_
+#define V8_LOGGING_TRACING_FLAGS_H_
+
+#include <atomic>
+
+#include "src/base/macros.h"
+
+namespace v8 {
+namespace internal {
+
+// This struct contains a set of flags that can be modified from multiple
+// threads at runtime unlike the normal FLAG_-like flags which are not modified
+// after V8 instance is initialized.
+
+struct TracingFlags {
+  static V8_EXPORT_PRIVATE std::atomic_uint runtime_stats;
+  static V8_EXPORT_PRIVATE std::atomic_uint gc;
+  static V8_EXPORT_PRIVATE std::atomic_uint gc_stats;
+  static V8_EXPORT_PRIVATE std::atomic_uint ic_stats;
+  static V8_EXPORT_PRIVATE std::atomic_uint zone_stats;
+
+  static bool is_runtime_stats_enabled() {
+    return runtime_stats.load(std::memory_order_relaxed) != 0;
+  }
+
+  static bool is_gc_enabled() {
+    return gc.load(std::memory_order_relaxed) != 0;
+  }
+
+  static bool is_gc_stats_enabled() {
+    return gc_stats.load(std::memory_order_relaxed) != 0;
+  }
+
+  static bool is_ic_stats_enabled() {
+    return ic_stats.load(std::memory_order_relaxed) != 0;
+  }
+
+  static bool is_zone_stats_enabled() {
+    return zone_stats.load(std::memory_order_relaxed) != 0;
+  }
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_LOGGING_TRACING_FLAGS_H_

src/tracing/trace-categories.h

@@ -47,6 +47,7 @@ PERFETTO_DEFINE_CATEGORIES(
     perfetto::Category(TRACE_DISABLED_BY_DEFAULT("v8.runtime_stats_sampling")),
     perfetto::Category(TRACE_DISABLED_BY_DEFAULT("v8.turbofan")),
     perfetto::Category(TRACE_DISABLED_BY_DEFAULT("v8.wasm")),
+    perfetto::Category(TRACE_DISABLED_BY_DEFAULT("v8.zone_stats")),
     perfetto::Category::Group("v8,devtools.timeline"),
     perfetto::Category::Group(TRACE_DISABLED_BY_DEFAULT("v8.turbofan") ","
                               TRACE_DISABLED_BY_DEFAULT("v8.wasm")));

src/tracing/tracing-category-observer.cc

@@ -57,6 +57,13 @@ void TracingCategoryObserver::OnTraceEnabled() {
     i::TracingFlags::ic_stats.fetch_or(ENABLED_BY_TRACING,
                                        std::memory_order_relaxed);
   }
+
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("v8.zone_stats"),
+                                     &enabled);
+  if (enabled) {
+    i::TracingFlags::zone_stats.fetch_or(ENABLED_BY_TRACING,
+                                         std::memory_order_relaxed);
+  }
 }
 
 void TracingCategoryObserver::OnTraceDisabled() {