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Merge pull request #7494 from Morph1984/no-time-to-wait

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native_clock: Wait for less time in EstimateRDTSCFrequency
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Fernando S 2021-12-05 18:56:38 +01:00 committed by GitHub
commit f1f91ad468
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1 changed files with 18 additions and 18 deletions
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36
src/common/x64/native_clock.cpp
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@ -15,26 +15,26 @@
namespace Common {
u64 EstimateRDTSCFrequency() {
const auto milli_10 = std::chrono::milliseconds{10};
// get current time
// Discard the first result measuring the rdtsc.
_mm_mfence();
const u64 tscStart = __rdtsc();
const auto startTime = std::chrono::steady_clock::now();
// wait roughly 3 seconds
while (true) {
auto milli = std::chrono::duration_cast<std::chrono::milliseconds>(
std::chrono::steady_clock::now() - startTime);
if (milli.count() >= 3000)
break;
std::this_thread::sleep_for(milli_10);
}
const auto endTime = std::chrono::steady_clock::now();
__rdtsc();
std::this_thread::sleep_for(std::chrono::milliseconds{1});
_mm_mfence();
const u64 tscEnd = __rdtsc();
// calculate difference
const u64 timer_diff =
std::chrono::duration_cast<std::chrono::nanoseconds>(endTime - startTime).count();
const u64 tsc_diff = tscEnd - tscStart;
__rdtsc();
// Get the current time.
const auto start_time = std::chrono::steady_clock::now();
_mm_mfence();
const u64 tsc_start = __rdtsc();
// Wait for 200 milliseconds.
std::this_thread::sleep_for(std::chrono::milliseconds{200});
const auto end_time = std::chrono::steady_clock::now();
_mm_mfence();
const u64 tsc_end = __rdtsc();
// Calculate differences.
const u64 timer_diff = static_cast<u64>(
std::chrono::duration_cast<std::chrono::nanoseconds>(end_time - start_time).count());
const u64 tsc_diff = tsc_end - tsc_start;
const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, timer_diff);
return tsc_freq;
}