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Common: improve native clock.

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This commit is contained in:
Fernando Sahmkow 2021-11-23 03:29:00 +01:00
parent c78f6d4f20
commit 096366ead5
3 changed files with 29 additions and 29 deletions
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5
src/common/uint128.h
View File

@ -30,6 +30,10 @@ namespace Common {
#else
return _udiv128(r[1], r[0], d, &remainder);
#endif
#else
#ifdef __SIZEOF_INT128__
const auto product = static_cast<unsigned __int128>(a) * static_cast<unsigned __int128>(b);
return static_cast<u64>(product / d);
#else
const u64 diva = a / d;
const u64 moda = a % d;
@ -37,6 +41,7 @@ namespace Common {
const u64 modb = b % d;
return diva * b + moda * divb + moda * modb / d;
#endif
#endif
}
// This function multiplies 2 u64 values and produces a u128 value;

40
src/common/x64/native_clock.cpp
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@ -5,7 +5,6 @@
#include <chrono>
#include <thread>
#include "common/atomic_ops.h"
#include "common/uint128.h"
#include "common/x64/native_clock.h"
@ -65,8 +64,10 @@ 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_} {
time_point.inner.last_measure = FencedRDTSC();
time_point.inner.accumulated_ticks = 0U;
TimePoint new_time_point{};
new_time_point.last_measure = FencedRDTSC();
new_time_point.accumulated_ticks = 0U;
time_point.store(new_time_point);
ns_rtsc_factor = GetFixedPoint64Factor(NS_RATIO, rtsc_frequency);
us_rtsc_factor = GetFixedPoint64Factor(US_RATIO, rtsc_frequency);
ms_rtsc_factor = GetFixedPoint64Factor(MS_RATIO, rtsc_frequency);
@ -76,34 +77,31 @@ NativeClock::NativeClock(u64 emulated_cpu_frequency_, u64 emulated_clock_frequen
u64 NativeClock::GetRTSC() {
TimePoint new_time_point{};
TimePoint current_time_point{};
current_time_point.pack = Common::AtomicLoad128(time_point.pack.data());
TimePoint current_time_point = time_point.load(std::memory_order_acquire);
do {
const u64 current_measure = FencedRDTSC();
u64 diff = current_measure - current_time_point.inner.last_measure;
u64 diff = current_measure - current_time_point.last_measure;
diff = diff & ~static_cast<u64>(static_cast<s64>(diff) >> 63); // max(diff, 0)
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));
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));
/// The clock cannot be more precise than the guest timer, remove the lower bits
return new_time_point.inner.accumulated_ticks & inaccuracy_mask;
return new_time_point.accumulated_ticks & inaccuracy_mask;
}
void NativeClock::Pause(bool is_paused) {
if (!is_paused) {
TimePoint current_time_point{};
TimePoint new_time_point{};
current_time_point.pack = Common::AtomicLoad128(time_point.pack.data());
TimePoint current_time_point = time_point.load(std::memory_order_acquire);
do {
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));
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));
}
}

13
src/common/x64/native_clock.h
View File

@ -3,6 +3,7 @@
#pragma once
#include <atomic>
#include "common/wall_clock.h"
namespace Common {
@ -28,13 +29,9 @@ public:
private:
u64 GetRTSC();
union alignas(16) TimePoint {
TimePoint() : pack{} {}
u128 pack{};
struct Inner {
u64 last_measure{};
u64 accumulated_ticks{};
} inner;
struct alignas(16) TimePoint {
u64 last_measure{};
u64 accumulated_ticks{};
};
/// value used to reduce the native clocks accuracy as some apss rely on
@ -42,7 +39,7 @@ private:
/// be higher.
static constexpr u64 inaccuracy_mask = ~(UINT64_C(0x400) - 1);
TimePoint time_point;
std::atomic<TimePoint> time_point;
// factors
u64 clock_rtsc_factor{};
u64 cpu_rtsc_factor{};