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Unified Diff: src/platform/time.cc

Issue 25468003: Always use timeGetTime() for TimeTicks::Now() on Windows. (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: REBASE Created 7 years, 2 months ago
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Index: src/platform/time.cc
diff --git a/src/platform/time.cc b/src/platform/time.cc
index ea6dd2c0bae6cfea3fc947b4c6f841c91a58b875..de0ca16473f6b5106485508653cfe797f6632c37 100644
--- a/src/platform/time.cc
+++ b/src/platform/time.cc
@@ -43,13 +43,6 @@
#include "win32-headers.h"
#endif
-#if V8_OS_WIN
-// Prototype for GetTickCount64() procedure.
-extern "C" {
-typedef ULONGLONG (WINAPI *GETTICKCOUNT64PROC)(void);
-}
-#endif
-
namespace v8 {
namespace internal {
@@ -175,43 +168,43 @@ struct timespec TimeDelta::ToTimespec() const {
// periodically resync the internal clock to the system clock.
class Clock V8_FINAL {
public:
- Clock() : initial_time_(CurrentWallclockTime()),
- initial_ticks_(TimeTicks::Now()) {}
+ Clock() : initial_ticks_(GetSystemTicks()), initial_time_(GetSystemTime()) {}
Time Now() {
- // This must be executed under lock.
- LockGuard<Mutex> lock_guard(&mutex_);
+ // Time between resampling the un-granular clock for this API (1 minute).
+ const TimeDelta kMaxElapsedTime = TimeDelta::FromMinutes(1);
- // Calculate the time elapsed since we started our timer.
- TimeDelta elapsed = TimeTicks::Now() - initial_ticks_;
+ LockGuard<Mutex> lock_guard(&mutex_);
- // Check if we don't need to synchronize with the wallclock yet.
- if (elapsed.InMicroseconds() <= kMaxMicrosecondsToAvoidDrift) {
- return initial_time_ + elapsed;
+ // Determine current time and ticks.
+ TimeTicks ticks = GetSystemTicks();
+ Time time = GetSystemTime();
+
+ // Check if we need to synchronize with the system clock due to a backwards
+ // time change or the amount of time elapsed.
+ TimeDelta elapsed = ticks - initial_ticks_;
+ if (time < initial_time_ || elapsed > kMaxElapsedTime) {
+ initial_ticks_ = ticks;
+ initial_time_ = time;
+ return time;
}
- // Resynchronize with the wallclock.
- initial_ticks_ = TimeTicks::Now();
- initial_time_ = CurrentWallclockTime();
- return initial_time_;
+ return initial_time_ + elapsed;
}
Time NowFromSystemTime() {
- // This must be executed under lock.
LockGuard<Mutex> lock_guard(&mutex_);
-
- // Resynchronize with the wallclock.
- initial_ticks_ = TimeTicks::Now();
- initial_time_ = CurrentWallclockTime();
+ initial_ticks_ = GetSystemTicks();
+ initial_time_ = GetSystemTime();
return initial_time_;
}
private:
- // Time between resampling the un-granular clock for this API (1 minute).
- static const int64_t kMaxMicrosecondsToAvoidDrift =
- Time::kMicrosecondsPerMinute;
+ static TimeTicks GetSystemTicks() {
+ return TimeTicks::Now();
+ }
- static Time CurrentWallclockTime() {
+ static Time GetSystemTime() {
FILETIME ft;
::GetSystemTimeAsFileTime(&ft);
return Time::FromFiletime(ft);
@@ -223,9 +216,9 @@ class Clock V8_FINAL {
};
-static LazyDynamicInstance<Clock,
- DefaultCreateTrait<Clock>,
- ThreadSafeInitOnceTrait>::type clock = LAZY_DYNAMIC_INSTANCE_INITIALIZER;
+static LazyStaticInstance<Clock,
+ DefaultConstructTrait<Clock>,
+ ThreadSafeInitOnceTrait>::type clock = LAZY_STATIC_INSTANCE_INITIALIZER;
Time Time::Now() {
@@ -388,6 +381,7 @@ class TickClock {
public:
virtual ~TickClock() {}
virtual int64_t Now() = 0;
+ virtual bool IsHighResolution() = 0;
};
@@ -440,42 +434,24 @@ class HighResolutionTickClock V8_FINAL : public TickClock {
int64_t ticks = (whole_seconds * Time::kMicrosecondsPerSecond) +
((leftover_ticks * Time::kMicrosecondsPerSecond) / ticks_per_second_);
- // Make sure we never return 0 here, so that TimeTicks::HighResNow()
+ // Make sure we never return 0 here, so that TimeTicks::HighResolutionNow()
// will never return 0.
return ticks + 1;
}
- private:
- int64_t ticks_per_second_;
-};
-
-
-// The GetTickCount64() API is what we actually want for the regular tick
-// clock, but this is only available starting with Windows Vista.
-class WindowsVistaTickClock V8_FINAL : public TickClock {
- public:
- explicit WindowsVistaTickClock(GETTICKCOUNT64PROC func) : func_(func) {
- ASSERT(func_ != NULL);
- }
- virtual ~WindowsVistaTickClock() {}
-
- virtual int64_t Now() V8_OVERRIDE {
- // Query the current ticks (in ms).
- ULONGLONG tick_count_ms = (*func_)();
-
- // Convert to microseconds (make sure to never return 0 here).
- return (tick_count_ms * Time::kMicrosecondsPerMillisecond) + 1;
+ virtual bool IsHighResolution() V8_OVERRIDE {
+ return true;
}
private:
- GETTICKCOUNT64PROC func_;
+ int64_t ticks_per_second_;
};
class RolloverProtectedTickClock V8_FINAL : public TickClock {
public:
// We initialize rollover_ms_ to 1 to ensure that we will never
- // return 0 from TimeTicks::HighResNow() and TimeTicks::Now() below.
+ // return 0 from TimeTicks::HighResolutionNow() and TimeTicks::Now() below.
RolloverProtectedTickClock() : last_seen_now_(0), rollover_ms_(1) {}
virtual ~RolloverProtectedTickClock() {}
@@ -487,6 +463,9 @@ class RolloverProtectedTickClock V8_FINAL : public TickClock {
// Note that we do not use GetTickCount() here, since timeGetTime() gives
// more predictable delta values, as described here:
// http://blogs.msdn.com/b/larryosterman/archive/2009/09/02/what-s-the-difference-between-gettickcount-and-timegettime.aspx
+ // timeGetTime() provides 1ms granularity when combined with
+ // timeBeginPeriod(). If the host application for V8 wants fast timers, it
+ // can use timeBeginPeriod() to increase the resolution.
DWORD now = timeGetTime();
if (now < last_seen_now_) {
rollover_ms_ += V8_INT64_C(0x100000000); // ~49.7 days.
@@ -495,6 +474,10 @@ class RolloverProtectedTickClock V8_FINAL : public TickClock {
return (now + rollover_ms_) * Time::kMicrosecondsPerMillisecond;
}
+ virtual bool IsHighResolution() V8_OVERRIDE {
+ return false;
+ }
+
private:
Mutex mutex_;
DWORD last_seen_now_;
@@ -502,27 +485,10 @@ class RolloverProtectedTickClock V8_FINAL : public TickClock {
};
-struct CreateTickClockTrait {
- static TickClock* Create() {
- // Try to load GetTickCount64() from kernel32.dll (available since Vista).
- HMODULE kernel32 = ::GetModuleHandleA("kernel32.dll");
- ASSERT(kernel32 != NULL);
- FARPROC proc = ::GetProcAddress(kernel32, "GetTickCount64");
- if (proc != NULL) {
- return new WindowsVistaTickClock(
- reinterpret_cast<GETTICKCOUNT64PROC>(proc));
- }
-
- // Fallback to the rollover protected tick clock.
- return new RolloverProtectedTickClock;
- }
-};
-
-
-static LazyDynamicInstance<TickClock,
- CreateTickClockTrait,
+static LazyStaticInstance<RolloverProtectedTickClock,
+ DefaultConstructTrait<RolloverProtectedTickClock>,
ThreadSafeInitOnceTrait>::type tick_clock =
- LAZY_DYNAMIC_INSTANCE_INITIALIZER;
+ LAZY_STATIC_INSTANCE_INITIALIZER;
struct CreateHighResTickClockTrait {
@@ -560,21 +526,27 @@ TimeTicks TimeTicks::Now() {
}
-TimeTicks TimeTicks::HighResNow() {
+TimeTicks TimeTicks::HighResolutionNow() {
// Make sure we never return 0 here.
TimeTicks ticks(high_res_tick_clock.Pointer()->Now());
ASSERT(!ticks.IsNull());
return ticks;
}
+
+// static
+bool TimeTicks::IsHighResolutionClockWorking() {
+ return high_res_tick_clock.Pointer()->IsHighResolution();
+}
+
#else // V8_OS_WIN
TimeTicks TimeTicks::Now() {
- return HighResNow();
+ return HighResolutionNow();
}
-TimeTicks TimeTicks::HighResNow() {
+TimeTicks TimeTicks::HighResolutionNow() {
int64_t ticks;
#if V8_OS_MACOSX
static struct mach_timebase_info info;
@@ -608,6 +580,12 @@ TimeTicks TimeTicks::HighResNow() {
return TimeTicks(ticks + 1);
}
+
+// static
+bool TimeTicks::IsHighResolutionClockWorking() {
+ return true;
+}
+
#endif // V8_OS_WIN
} } // namespace v8::internal
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