native_clock: Round RDTSC frequency to the nearest 1000
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026eaddbee
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@ -6,6 +6,7 @@
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#include <thread>
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#include <thread>
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#include "common/atomic_ops.h"
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#include "common/atomic_ops.h"
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#include "common/steady_clock.h"
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#include "common/uint128.h"
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#include "common/uint128.h"
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#include "common/x64/native_clock.h"
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#include "common/x64/native_clock.h"
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@ -39,6 +40,12 @@ static u64 FencedRDTSC() {
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}
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}
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#endif
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#endif
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template <u64 Nearest>
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static u64 RoundToNearest(u64 value) {
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const auto mod = value % Nearest;
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return mod >= (Nearest / 2) ? (value - mod + Nearest) : (value - mod);
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}
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u64 EstimateRDTSCFrequency() {
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u64 EstimateRDTSCFrequency() {
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// Discard the first result measuring the rdtsc.
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// Discard the first result measuring the rdtsc.
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FencedRDTSC();
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FencedRDTSC();
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@ -46,18 +53,18 @@ u64 EstimateRDTSCFrequency() {
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FencedRDTSC();
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FencedRDTSC();
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// Get the current time.
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// Get the current time.
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const auto start_time = std::chrono::steady_clock::now();
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const auto start_time = Common::SteadyClock::Now();
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const u64 tsc_start = FencedRDTSC();
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const u64 tsc_start = FencedRDTSC();
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// Wait for 200 milliseconds.
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// Wait for 250 milliseconds.
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std::this_thread::sleep_for(std::chrono::milliseconds{200});
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std::this_thread::sleep_for(std::chrono::milliseconds{250});
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const auto end_time = std::chrono::steady_clock::now();
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const auto end_time = Common::SteadyClock::Now();
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const u64 tsc_end = FencedRDTSC();
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const u64 tsc_end = FencedRDTSC();
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// Calculate differences.
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// Calculate differences.
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const u64 timer_diff = static_cast<u64>(
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const u64 timer_diff = static_cast<u64>(
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std::chrono::duration_cast<std::chrono::nanoseconds>(end_time - start_time).count());
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std::chrono::duration_cast<std::chrono::nanoseconds>(end_time - start_time).count());
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const u64 tsc_diff = tsc_end - tsc_start;
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const u64 tsc_diff = tsc_end - tsc_start;
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const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, timer_diff);
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const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, timer_diff);
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return tsc_freq;
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return RoundToNearest<1000>(tsc_freq);
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}
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}
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namespace X64 {
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namespace X64 {
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