40 lines
1.3 KiB
C++
40 lines
1.3 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/steady_clock.h"
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#include "common/uint128.h"
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#include "common/x64/rdtsc.h"
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namespace Common::X64 {
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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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// 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 = RealTimeClock::Now();
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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 = RealTimeClock::Now();
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const u64 tsc_end = FencedRDTSC();
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// Calculate differences.
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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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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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return RoundToNearest<100'000>(tsc_freq);
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}
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} // namespace Common::X64
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