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Unified Diff: base/time/time_win_unittest.cc

Issue 797893003: [Windows] One TimeTicks clock: efficient/reliable high-res, with low-res fallback. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Better testing of TimeTicks::FromQPCValue(). Created 5 years, 11 months ago
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Index: base/time/time_win_unittest.cc
diff --git a/base/time/time_win_unittest.cc b/base/time/time_win_unittest.cc
index 058dfd79d147d6f6092bfc17680b1fc75a0583ff..48a3560fb9147330f00f9bf8e2a74b286b789a2e 100644
--- a/base/time/time_win_unittest.cc
+++ b/base/time/time_win_unittest.cc
@@ -6,6 +6,8 @@
#include <mmsystem.h>
#include <process.h>
+#include <cmath>
+
#include "base/threading/platform_thread.h"
#include "base/time/time.h"
#include "testing/gtest/include/gtest/gtest.h"
@@ -114,7 +116,7 @@ TEST(TimeTicks, WinRollover) {
TEST(TimeTicks, SubMillisecondTimers) {
// HighResNow doesn't work on some systems. Since the product still works
// even if it doesn't work, it makes this entire test questionable.
- if (!TimeTicks::IsHighResClockWorking())
+ if (!TimeTicks::IsHighResolution())
return;
const int kRetries = 1000;
@@ -183,7 +185,7 @@ TEST(TimeTicks, TimerPerformance) {
TestCase cases[] = {
{ reinterpret_cast<TestFunc>(Time::Now), "Time::Now" },
{ TimeTicks::Now, "TimeTicks::Now" },
- { TimeTicks::HighResNow, "TimeTicks::HighResNow" },
+ { TimeTicks::NowFromSystemTraceTime, "TimeTicks::NowFromSystemTraceTime" },
{ NULL, "" }
};
@@ -207,65 +209,47 @@ TEST(TimeTicks, TimerPerformance) {
}
}
-// http://crbug.com/396384
-TEST(TimeTicks, DISABLED_Drift) {
- // If QPC is disabled, this isn't measuring anything.
- if (!TimeTicks::IsHighResClockWorking())
+TEST(TimeTicks, FromQPCValue) {
+ if (!TimeTicks::IsHighResolution())
return;
const int kIterations = 100;
- int64 total_drift = 0;
-
- for (int i = 0; i < kIterations; ++i) {
- int64 drift_microseconds = TimeTicks::GetQPCDriftMicroseconds();
- // Make sure the drift never exceeds our limit.
- EXPECT_LT(drift_microseconds, 50000);
-
- // Sleep for a few milliseconds (note that it means 1000 microseconds).
- // If we check the drift too frequently, it's going to increase
- // monotonically, making our measurement less realistic.
- base::PlatformThread::Sleep(
- base::TimeDelta::FromMilliseconds((i % 2 == 0) ? 1 : 2));
+ LARGE_INTEGER frequency;
+ ASSERT_TRUE(QueryPerformanceFrequency(&frequency));
+ const int64 ticks_per_second = frequency.QuadPart;
+ ASSERT_GT(ticks_per_second, 0);
+
+ // Tolerance between the TimeTicks values computed by this test versus those
+ // computed using FromQCPValue(). On most systems, this will be 1us.
+ // However, when the QPC frequency is less than 1 MHz, the tolerance needs to
+ // be greater.
+ const int64 tolerance_us = static_cast<int64>(
+ std::ceil((1.0 / ticks_per_second) * Time::kMicrosecondsPerSecond));
+
+ int64 ticks_increment = 10; // Changes with each loop iteration.
+ LARGE_INTEGER start_ticks;
+ // The start value is chosen such that part of the test will make
+ // FromQPCValue() use the faster conversion logic, and part will make it use
+ // the overflow-safe logic.
+ start_ticks.QuadPart =
+ Time::kQPCOverflowThreshold - (ticks_increment * kIterations / 2);
+ LARGE_INTEGER ticks = start_ticks;
+ TimeTicks start_time = TimeTicks() + TimeDelta::FromMicroseconds(
+ start_ticks.QuadPart * Time::kMicrosecondsPerSecond / ticks_per_second);
- total_drift += drift_microseconds;
+ for (int i = 0; i < kIterations; ++i) {
brianderson 2015/01/09 00:02:02 I don't think this for loop tests the 3 corner cas
miu 2015/01/14 02:12:24 Done.
+ ticks.QuadPart += ticks_increment;
+ ticks_increment = ticks_increment * 6 / 5;
+
+ const int64 ticks_advanced = ticks.QuadPart - start_ticks.QuadPart;
+ const TimeTicks expected_value = start_time +
brianderson 2015/01/09 00:02:02 This test rounds to microseconds twice (here and i
miu 2015/01/14 02:12:24 I looked into 128-bit integers, but didn't like wh
brianderson 2015/01/14 02:31:42 Thanks for looking into that. It would have been n
+ TimeDelta::FromMicroseconds(
+ ticks_advanced * Time::kMicrosecondsPerSecond / ticks_per_second);
+ const TimeTicks value = TimeTicks::FromQPCValue(ticks.QuadPart);
+ EXPECT_GE(tolerance_us,
+ (value - expected_value).magnitude().InMicroseconds())
+ << "iteration: " << i << ", logic path: "
+ << (ticks.QuadPart < Time::kQPCOverflowThreshold ? "FAST" : "SAFE");
}
-
- // Sanity check. We expect some time drift to occur, especially across
- // the number of iterations we do.
- EXPECT_LT(0, total_drift);
-
- printf("average time drift in microseconds: %lld\n",
- total_drift / kIterations);
-}
-
-int64 QPCValueToMicrosecondsSafely(LONGLONG qpc_value,
- int64 ticks_per_second) {
- int64 whole_seconds = qpc_value / ticks_per_second;
- int64 leftover_ticks = qpc_value % ticks_per_second;
- int64 microseconds = (whole_seconds * Time::kMicrosecondsPerSecond) +
- ((leftover_ticks * Time::kMicrosecondsPerSecond) /
- ticks_per_second);
- return microseconds;
-}
-
-TEST(TimeTicks, FromQPCValue) {
- if (!TimeTicks::IsHighResClockWorking())
- return;
- LARGE_INTEGER frequency;
- QueryPerformanceFrequency(&frequency);
- int64 ticks_per_second = frequency.QuadPart;
- LONGLONG qpc_value = Time::kQPCOverflowThreshold;
- TimeTicks expected_value = TimeTicks::FromInternalValue(
- QPCValueToMicrosecondsSafely(qpc_value + 1, ticks_per_second));
- EXPECT_EQ(expected_value,
- TimeTicks::FromQPCValue(qpc_value + 1));
- expected_value = TimeTicks::FromInternalValue(
- QPCValueToMicrosecondsSafely(qpc_value, ticks_per_second));
- EXPECT_EQ(expected_value,
- TimeTicks::FromQPCValue(qpc_value));
- expected_value = TimeTicks::FromInternalValue(
- QPCValueToMicrosecondsSafely(qpc_value - 1, ticks_per_second));
- EXPECT_EQ(expected_value,
- TimeTicks::FromQPCValue(qpc_value - 1));
}
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