[counters] CPU time for RCS

The newly introduced --rcs-cpu-time flag enables CPU time for all
runtime call stats timers. By default we still keep on using good
old wall time.

This CL also adds the long-awaited --rcs short flag.

Change-Id: I3173e3a0f846ec3bf0d319624a37741c56914be5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2060304Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66427}

src/flags/flag-definitions.h

@@ -1289,6 +1289,12 @@ DEFINE_GENERIC_IMPLICATION(
     runtime_call_stats,
     TracingFlags::runtime_stats.store(
         v8::tracing::TracingCategoryObserver::ENABLED_BY_NATIVE))
+DEFINE_BOOL(rcs, false, "report runtime call counts and times")
+DEFINE_IMPLICATION(rcs, runtime_call_stats)
+
+DEFINE_BOOL(rcs_cpu_time, false,
+            "report runtime times in cpu time (the default is wall time)")
+DEFINE_IMPLICATION(rcs_cpu_time, rcs)
 
 // snapshot-common.cc
 DEFINE_BOOL(profile_deserialization, false,

src/logging/counters.cc

@@ -319,6 +319,11 @@ void Counters::ResetCreateHistogramFunction(CreateHistogramCallback f) {
 base::TimeTicks (*RuntimeCallTimer::Now)() =
     &base::TimeTicks::HighResolutionNow;
 
+base::TimeTicks RuntimeCallTimer::NowCPUTime() {
+  base::ThreadTicks ticks = base::ThreadTicks::Now();
+  return base::TimeTicks::FromInternalValue(ticks.ToInternalValue());
+}
+
 class RuntimeCallStatEntries {
  public:
   void Print(std::ostream& os) {
@@ -454,6 +459,11 @@ RuntimeCallStats::RuntimeCallStats(ThreadType thread_type)
   for (int i = 0; i < kNumberOfCounters; i++) {
     this->counters_[i] = RuntimeCallCounter(kNames[i]);
   }
+  if (FLAG_rcs_cpu_time) {
+    CHECK(base::ThreadTicks::IsSupported());
+    base::ThreadTicks::WaitUntilInitialized();
+    RuntimeCallTimer::Now = &RuntimeCallTimer::NowCPUTime;
+  }
 }
 
 namespace {

src/logging/counters.h

@@ -714,6 +714,9 @@ class RuntimeCallTimer final {
   // Make the time source configurable for testing purposes.
   V8_EXPORT_PRIVATE static base::TimeTicks (*Now)();
 
+  // Helper to switch over to CPU time.
+  static base::TimeTicks NowCPUTime();
+
  private:
   inline void Pause(base::TimeTicks now);
   inline void Resume(base::TimeTicks now);