The precision of sleep_for and wait_for is limited to 1-1.5ms on Windows. Using SleepForOneTick() allows us to sleep for exactly one interval of the current timer resolution. This allows us to take advantage of systems that have a timer resolution of 0.5ms to reduce CPU overhead in the event loop.
89 lines
3.1 KiB
C++
89 lines
3.1 KiB
C++
// SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
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// SPDX-License-Identifier: GPL-2.0-or-later
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#include "common/steady_clock.h"
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#include "common/uint128.h"
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#include "common/wall_clock.h"
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#ifdef ARCHITECTURE_x86_64
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#include "common/x64/cpu_detect.h"
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#include "common/x64/native_clock.h"
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#endif
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namespace Common {
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class StandardWallClock final : public WallClock {
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public:
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explicit StandardWallClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequency_)
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: WallClock{emulated_cpu_frequency_, emulated_clock_frequency_, false},
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start_time{SteadyClock::Now()} {}
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std::chrono::nanoseconds GetTimeNS() override {
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return SteadyClock::Now() - start_time;
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}
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std::chrono::microseconds GetTimeUS() override {
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return std::chrono::duration_cast<std::chrono::microseconds>(GetTimeNS());
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}
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std::chrono::milliseconds GetTimeMS() override {
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return std::chrono::duration_cast<std::chrono::milliseconds>(GetTimeNS());
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}
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u64 GetClockCycles() override {
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const u128 temp = Common::Multiply64Into128(GetTimeNS().count(), emulated_clock_frequency);
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return Common::Divide128On32(temp, NS_RATIO).first;
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}
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u64 GetCPUCycles() override {
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const u128 temp = Common::Multiply64Into128(GetTimeNS().count(), emulated_cpu_frequency);
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return Common::Divide128On32(temp, NS_RATIO).first;
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}
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void Pause([[maybe_unused]] bool is_paused) override {
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// Do nothing in this clock type.
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}
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private:
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SteadyClock::time_point start_time;
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};
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#ifdef ARCHITECTURE_x86_64
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std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
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u64 emulated_clock_frequency) {
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const auto& caps = GetCPUCaps();
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u64 rtsc_frequency = 0;
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if (caps.invariant_tsc) {
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rtsc_frequency = caps.tsc_frequency ? caps.tsc_frequency : EstimateRDTSCFrequency();
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}
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// Fallback to StandardWallClock if the hardware TSC does not have the precision greater than:
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// - A nanosecond
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// - The emulated CPU frequency
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// - The emulated clock counter frequency (CNTFRQ)
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if (rtsc_frequency <= WallClock::NS_RATIO || rtsc_frequency <= emulated_cpu_frequency ||
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rtsc_frequency <= emulated_clock_frequency) {
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return std::make_unique<StandardWallClock>(emulated_cpu_frequency,
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emulated_clock_frequency);
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} else {
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return std::make_unique<X64::NativeClock>(emulated_cpu_frequency, emulated_clock_frequency,
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rtsc_frequency);
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}
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}
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#else
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std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
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u64 emulated_clock_frequency) {
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return std::make_unique<StandardWallClock>(emulated_cpu_frequency, emulated_clock_frequency);
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}
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#endif
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std::unique_ptr<WallClock> CreateStandardWallClock(u64 emulated_cpu_frequency,
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u64 emulated_clock_frequency) {
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return std::make_unique<StandardWallClock>(emulated_cpu_frequency, emulated_clock_frequency);
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}
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} // namespace Common
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