61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
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// SPDX-License-Identifier: GPL-2.0-or-later
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#include <thread>
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#include "common/rdtsc.h"
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#include "common/uint128.h"
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#ifdef _WIN64
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#include <windows.h>
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#endif
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namespace Common {
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static constexpr size_t SecondToNanoseconds = 1000000000ULL;
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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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static u64 GetTimeNs() {
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#ifdef _WIN64
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// GetSystemTimePreciseAsFileTime returns the file time in 100ns units.
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static constexpr u64 Multiplier = 100;
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// Convert Windows epoch to Unix epoch.
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static constexpr u64 WindowsEpochToUnixEpoch = 0x19DB1DED53E8000LL;
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FILETIME filetime;
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GetSystemTimePreciseAsFileTime(&filetime);
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return Multiplier * ((static_cast<u64>(filetime.dwHighDateTime) << 32) +
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static_cast<u64>(filetime.dwLowDateTime) - WindowsEpochToUnixEpoch);
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#elif defined(__APPLE__)
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return clock_gettime_nsec_np(CLOCK_REALTIME);
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#else
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timespec ts;
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clock_gettime(CLOCK_REALTIME, &ts);
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return ts.tv_sec * SecondToNanoseconds + ts.tv_nsec;
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#endif
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}
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u64 EstimateRDTSCFrequency() {
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// Discard the first result measuring the rdtsc.
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FencedRDTSC();
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std::this_thread::sleep_for(std::chrono::milliseconds{1});
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FencedRDTSC();
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// Get the current time.
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const auto start_time = GetTimeNs();
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const u64 tsc_start = FencedRDTSC();
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// Wait for 100 milliseconds.
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std::this_thread::sleep_for(std::chrono::milliseconds{100});
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const auto end_time = GetTimeNs();
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const u64 tsc_end = FencedRDTSC();
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// Calculate differences.
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const u64 tsc_diff = tsc_end - tsc_start;
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const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, end_time - start_time);
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return RoundToNearest<100'000>(tsc_freq);
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}
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} // namespace Common
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