[Reland] Implement CPU time for OS X and POSIX.

V8 tracing controller uses 2 clocks: wall clock and cpu clock. This patch
implements CPU time for OS X and POSIX to provide more accurate
accounting of CPU time used by each thread.

BUG=v8:4984
LOG=n

Review-Url: https://codereview.chromium.org/1966183003
Cr-Commit-Position: refs/heads/master@{#36213}

src/base/platform/time.cc

@@ -10,7 +10,9 @@
 #include <unistd.h>
 #endif
 #if V8_OS_MACOSX
+#include <mach/mach.h>
 #include <mach/mach_time.h>
+#include <pthread.h>
 #endif
 
 #include <cstring>
@@ -25,6 +27,51 @@
 #include "src/base/logging.h"
 #include "src/base/platform/platform.h"
 
+namespace {
+
+#if V8_OS_MACOSX
+int64_t ComputeThreadTicks() {
+  mach_msg_type_number_t thread_info_count = THREAD_BASIC_INFO_COUNT;
+  thread_basic_info_data_t thread_info_data;
+  kern_return_t kr = thread_info(
+      pthread_mach_thread_np(pthread_self()),
+      THREAD_BASIC_INFO,
+      reinterpret_cast<thread_info_t>(&thread_info_data),
+      &thread_info_count);
+  CHECK(kr == KERN_SUCCESS);
+
+  v8::base::CheckedNumeric<int64_t> absolute_micros(
+      thread_info_data.user_time.seconds);
+  absolute_micros *= v8::base::Time::kMicrosecondsPerSecond;
+  absolute_micros += thread_info_data.user_time.microseconds;
+  return absolute_micros.ValueOrDie();
+}
+#elif V8_OS_POSIX
+// Helper function to get results from clock_gettime() and convert to a
+// microsecond timebase. Minimum requirement is MONOTONIC_CLOCK to be supported
+// on the system. FreeBSD 6 has CLOCK_MONOTONIC but defines
+// _POSIX_MONOTONIC_CLOCK to -1.
+inline int64_t ClockNow(clockid_t clk_id) {
+#if (defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0) || \
+  defined(V8_OS_BSD) || defined(V8_OS_ANDROID)
+  struct timespec ts;
+  if (clock_gettime(clk_id, &ts) != 0) {
+    UNREACHABLE();
+    return 0;
+  }
+  v8::base::internal::CheckedNumeric<int64_t> result(ts.tv_sec);
+  result *= v8::base::Time::kMicrosecondsPerSecond;
+  result += (ts.tv_nsec / v8::base::Time::kNanosecondsPerMicrosecond);
+  return result.ValueOrDie();
+#else  // Monotonic clock not supported.
+  return 0;
+#endif
+}
+#endif  // V8_OS_MACOSX
+
+
+}  // namespace
+
 namespace v8 {
 namespace base {
 
@@ -541,12 +588,7 @@ TimeTicks TimeTicks::HighResolutionNow() {
 #elif V8_OS_SOLARIS
   ticks = (gethrtime() / Time::kNanosecondsPerMicrosecond);
 #elif V8_OS_POSIX
-  struct timespec ts;
+  ticks = ClockNow(CLOCK_MONOTONIC);
-  int result = clock_gettime(CLOCK_MONOTONIC, &ts);
-  DCHECK_EQ(0, result);
-  USE(result);
-  ticks = (ts.tv_sec * Time::kMicrosecondsPerSecond +
-           ts.tv_nsec / Time::kNanosecondsPerMicrosecond);
 #endif  // V8_OS_MACOSX
   // Make sure we never return 0 here.
   return TimeTicks(ticks + 1);
@@ -560,5 +602,30 @@ bool TimeTicks::IsHighResolutionClockWorking() {
 
 #endif  // V8_OS_WIN
 
+
+// TODO(lpy): For windows ThreadTicks implementation,
+// see http://crbug.com/v8/5000
+bool ThreadTicks::IsSupported() {
+#if (defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
+    defined(V8_OS_MACOSX) || defined(V8_OS_ANDROID)
+    return true;
+#else
+    return false;
+#endif
+}
+
+
+ThreadTicks ThreadTicks::Now() {
+#if V8_OS_MACOSX
+  return ThreadTicks(ComputeThreadTicks());
+#elif(defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
+  defined(V8_OS_ANDROID)
+  return ThreadTicks(ClockNow(CLOCK_THREAD_CPUTIME_ID));
+#else
+  UNREACHABLE();
+  return ThreadTicks();
+#endif
+}
+
 }  // namespace base
 }  // namespace v8

src/base/platform/time.h

@@ -360,7 +360,7 @@ class TimeTicks final : public time_internal::TimeBase<TimeTicks> {
   friend class time_internal::TimeBase<TimeTicks>;
 
   // Please use Now() to create a new object. This is for internal use
-  // and testing. Ticks is in microseconds.
+  // and testing. Ticks are in microseconds.
   explicit TimeTicks(int64_t ticks) : TimeBase(ticks) {}
 };
 
@@ -368,6 +368,31 @@ inline TimeTicks operator+(const TimeDelta& delta, const TimeTicks& ticks) {
   return ticks + delta;
 }
 
+
+// ThreadTicks ----------------------------------------------------------------
+
+// Represents a clock, specific to a particular thread, than runs only while the
+// thread is running.
+class ThreadTicks final : public time_internal::TimeBase<ThreadTicks> {
+ public:
+  ThreadTicks() : TimeBase(0) {}
+
+  // Returns true if ThreadTicks::Now() is supported on this system.
+  static bool IsSupported();
+
+  // Returns thread-specific CPU-time on systems that support this feature.
+  // Needs to be guarded with a call to IsSupported(). Use this timer
+  // to (approximately) measure how much time the calling thread spent doing
+  // actual work vs. being de-scheduled. May return bogus results if the thread
+  // migrates to another CPU between two calls. Returns an empty ThreadTicks
+  // object until the initialization is completed.
+  static ThreadTicks Now();
+
+ private:
+  // This is for internal use and testing. Ticks are in microseconds.
+  explicit ThreadTicks(int64_t ticks) : TimeBase(ticks) {}
+};
+
 }  // namespace base
 }  // namespace v8
 

test/unittests/base/platform/time-unittest.cc

@@ -16,6 +16,7 @@
 #endif
 
 #include "src/base/platform/elapsed-timer.h"
+#include "src/base/platform/platform.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace v8 {
@@ -182,5 +183,32 @@ TEST(TimeTicks, IsMonotonic) {
   }
 }
 
+
+// Disable on windows until it is implemented.
+#if V8_OS_ANDROID || V8_OS_WIN
+#define MAYBE_ThreadNow DISABLED_ThreadNow
+#else
+#define MAYBE_ThreadNow ThreadNow
+#endif
+TEST(ThreadTicks, MAYBE_ThreadNow) {
+  if (ThreadTicks::IsSupported()) {
+    TimeTicks begin = TimeTicks::Now();
+    ThreadTicks begin_thread = ThreadTicks::Now();
+    // Make sure that ThreadNow value is non-zero.
+    EXPECT_GT(begin_thread, ThreadTicks());
+    // Sleep for 10 milliseconds to get the thread de-scheduled.
+    OS::Sleep(base::TimeDelta::FromMilliseconds(10));
+    ThreadTicks end_thread = ThreadTicks::Now();
+    TimeTicks end = TimeTicks::Now();
+    TimeDelta delta = end - begin;
+    TimeDelta delta_thread = end_thread - begin_thread;
+    // Make sure that some thread time have elapsed.
+    EXPECT_GT(delta_thread.InMicroseconds(), 0);
+    // But the thread time is at least 9ms less than clock time.
+    TimeDelta difference = delta - delta_thread;
+    EXPECT_GE(difference.InMicroseconds(), 9000);
+  }
+}
+
 }  // namespace base
 }  // namespace v8