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Native clock: Use atomic ops as before.

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This commit is contained in:
Fernando Sahmkow 2022-06-28 22:42:00 +02:00
parent f5c1d7b8c8
commit 2575a93dc6
2 changed files with 29 additions and 24 deletions
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39
src/common/x64/native_clock.cpp
View file

@ -65,10 +65,8 @@ NativeClock::NativeClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequen
u64 rtsc_frequency_)
: WallClock(emulated_cpu_frequency_, emulated_clock_frequency_, true), rtsc_frequency{
rtsc_frequency_} {
TimePoint new_time_point{};
new_time_point.last_measure = FencedRDTSC();
new_time_point.accumulated_ticks = 0U;
time_point.store(new_time_point);
time_point.inner.last_measure = FencedRDTSC();
time_point.inner.accumulated_ticks = 0U;
ns_rtsc_factor = GetFixedPoint64Factor(NS_RATIO, rtsc_frequency);
us_rtsc_factor = GetFixedPoint64Factor(US_RATIO, rtsc_frequency);
ms_rtsc_factor = GetFixedPoint64Factor(MS_RATIO, rtsc_frequency);
@ -77,32 +75,35 @@ NativeClock::NativeClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequen
}
u64 NativeClock::GetRTSC() {
TimePoint current_time_point{};
TimePoint new_time_point{};
TimePoint current_time_point = time_point.load(std::memory_order_acquire);
current_time_point.pack = Common::AtomicLoad128(time_point.pack.data());
do {
const u64 current_measure = FencedRDTSC();
u64 diff = current_measure - current_time_point.last_measure;
u64 diff = current_measure - current_time_point.inner.last_measure;
diff = diff & ~static_cast<u64>(static_cast<s64>(diff) >> 63); // max(diff, 0)
new_time_point.last_measure = current_measure > current_time_point.last_measure
? current_measure
: current_time_point.last_measure;
new_time_point.accumulated_ticks = current_time_point.accumulated_ticks + diff;
} while (!time_point.compare_exchange_weak(
current_time_point, new_time_point, std::memory_order_release, std::memory_order_acquire));
new_time_point.inner.last_measure = current_measure > current_time_point.inner.last_measure
? current_measure
: current_time_point.inner.last_measure;
new_time_point.inner.accumulated_ticks = current_time_point.inner.accumulated_ticks + diff;
} while (!Common::AtomicCompareAndSwap(time_point.pack.data(), new_time_point.pack,
current_time_point.pack, current_time_point.pack));
/// The clock cannot be more precise than the guest timer, remove the lower bits
return new_time_point.accumulated_ticks;
return new_time_point.inner.accumulated_ticks;
}
void NativeClock::Pause(bool is_paused) {
if (!is_paused) {
TimePoint current_time_point{};
TimePoint new_time_point{};
TimePoint current_time_point = time_point.load(std::memory_order_acquire);
current_time_point.pack = Common::AtomicLoad128(time_point.pack.data());
do {
new_time_point = current_time_point;
new_time_point.last_measure = FencedRDTSC();
} while (!time_point.compare_exchange_weak(current_time_point, new_time_point,
std::memory_order_release,
std::memory_order_acquire));
new_time_point.pack = current_time_point.pack;
new_time_point.inner.last_measure = FencedRDTSC();
} while (!Common::AtomicCompareAndSwap(time_point.pack.data(), new_time_point.pack,
current_time_point.pack, current_time_point.pack));
}
}

14
src/common/x64/native_clock.h
View file

@ -3,7 +3,6 @@
#pragma once
#include <atomic>
#include "common/wall_clock.h"
namespace Common {
@ -29,12 +28,17 @@ public:
private:
u64 GetRTSC();
struct alignas(16) TimePoint {
u64 last_measure{};
u64 accumulated_ticks{};
union alignas(16) TimePoint {
TimePoint() : pack{} {}
u128 pack{};
struct Inner {
u64 last_measure{};
u64 accumulated_ticks{};
} inner;
};
std::atomic<TimePoint> time_point;
TimePoint time_point;
// factors
u64 clock_rtsc_factor{};
u64 cpu_rtsc_factor{};