core_timing: Use higher precision sleeps on Windows

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.
This commit is contained in:
Morph 2023-03-01 21:06:19 -05:00
parent 7e353082ac
commit bff1453282
5 changed files with 47 additions and 24 deletions

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@ -81,4 +81,9 @@ std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
#endif
std::unique_ptr<WallClock> CreateStandardWallClock(u64 emulated_cpu_frequency,
u64 emulated_clock_frequency) {
return std::make_unique<StandardWallClock>(emulated_cpu_frequency, emulated_clock_frequency);
}
} // namespace Common

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@ -55,4 +55,7 @@ private:
[[nodiscard]] std::unique_ptr<WallClock> CreateBestMatchingClock(u64 emulated_cpu_frequency,
u64 emulated_clock_frequency);
[[nodiscard]] std::unique_ptr<WallClock> CreateStandardWallClock(u64 emulated_cpu_frequency,
u64 emulated_clock_frequency);
} // namespace Common

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@ -6,6 +6,10 @@
#include <string>
#include <tuple>
#ifdef _WIN32
#include "common/windows/timer_resolution.h"
#endif
#include "common/microprofile.h"
#include "core/core_timing.h"
#include "core/core_timing_util.h"
@ -38,7 +42,8 @@ struct CoreTiming::Event {
};
CoreTiming::CoreTiming()
: clock{Common::CreateBestMatchingClock(Hardware::BASE_CLOCK_RATE, Hardware::CNTFREQ)} {}
: cpu_clock{Common::CreateBestMatchingClock(Hardware::BASE_CLOCK_RATE, Hardware::CNTFREQ)},
event_clock{Common::CreateStandardWallClock(Hardware::BASE_CLOCK_RATE, Hardware::CNTFREQ)} {}
CoreTiming::~CoreTiming() {
Reset();
@ -185,15 +190,15 @@ void CoreTiming::ResetTicks() {
}
u64 CoreTiming::GetCPUTicks() const {
if (is_multicore) {
return clock->GetCPUCycles();
if (is_multicore) [[likely]] {
return cpu_clock->GetCPUCycles();
}
return ticks;
}
u64 CoreTiming::GetClockTicks() const {
if (is_multicore) {
return clock->GetClockCycles();
if (is_multicore) [[likely]] {
return cpu_clock->GetClockCycles();
}
return CpuCyclesToClockCycles(ticks);
}
@ -252,22 +257,21 @@ void CoreTiming::ThreadLoop() {
const auto next_time = Advance();
if (next_time) {
// There are more events left in the queue, wait until the next event.
const auto wait_time = *next_time - GetGlobalTimeNs().count();
auto wait_time = *next_time - GetGlobalTimeNs().count();
if (wait_time > 0) {
#ifdef _WIN32
// Assume a timer resolution of 1ms.
static constexpr s64 TimerResolutionNS = 1000000;
const auto timer_resolution_ns =
Common::Windows::GetCurrentTimerResolution().count();
// Sleep in discrete intervals of the timer resolution, and spin the rest.
const auto sleep_time = wait_time - (wait_time % TimerResolutionNS);
if (sleep_time > 0) {
event.WaitFor(std::chrono::nanoseconds(sleep_time));
}
while (!paused && !event.IsSet() && wait_time > 0) {
wait_time = *next_time - GetGlobalTimeNs().count();
while (!paused && !event.IsSet() && GetGlobalTimeNs().count() < *next_time) {
// Yield to reduce thread starvation.
if (wait_time >= timer_resolution_ns) {
Common::Windows::SleepForOneTick();
} else {
std::this_thread::yield();
}
}
if (event.IsSet()) {
event.Reset();
@ -285,9 +289,9 @@ void CoreTiming::ThreadLoop() {
}
paused_set = true;
clock->Pause(true);
event_clock->Pause(true);
pause_event.Wait();
clock->Pause(false);
event_clock->Pause(false);
}
}
@ -303,16 +307,23 @@ void CoreTiming::Reset() {
has_started = false;
}
std::chrono::nanoseconds CoreTiming::GetCPUTimeNs() const {
if (is_multicore) [[likely]] {
return cpu_clock->GetTimeNS();
}
return CyclesToNs(ticks);
}
std::chrono::nanoseconds CoreTiming::GetGlobalTimeNs() const {
if (is_multicore) {
return clock->GetTimeNS();
if (is_multicore) [[likely]] {
return event_clock->GetTimeNS();
}
return CyclesToNs(ticks);
}
std::chrono::microseconds CoreTiming::GetGlobalTimeUs() const {
if (is_multicore) {
return clock->GetTimeUS();
if (is_multicore) [[likely]] {
return event_clock->GetTimeUS();
}
return CyclesToUs(ticks);
}

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@ -122,6 +122,9 @@ public:
/// Returns current time in emulated in Clock cycles
u64 GetClockTicks() const;
/// Returns current time in nanoseconds.
std::chrono::nanoseconds GetCPUTimeNs() const;
/// Returns current time in microseconds.
std::chrono::microseconds GetGlobalTimeUs() const;
@ -139,7 +142,8 @@ private:
void Reset();
std::unique_ptr<Common::WallClock> clock;
std::unique_ptr<Common::WallClock> cpu_clock;
std::unique_ptr<Common::WallClock> event_clock;
s64 global_timer = 0;

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@ -197,7 +197,7 @@ struct GPU::Impl {
constexpr u64 gpu_ticks_num = 384;
constexpr u64 gpu_ticks_den = 625;
u64 nanoseconds = system.CoreTiming().GetGlobalTimeNs().count();
u64 nanoseconds = system.CoreTiming().GetCPUTimeNs().count();
if (Settings::values.use_fast_gpu_time.GetValue()) {
nanoseconds /= 256;
}