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native_clock: Use writeback from CAS to avoid double-loading

This commit is contained in:
merry 2022-04-02 21:05:49 +01:00
parent 084bd225dc
commit 979e53b87b
1 changed files with 6 additions and 4 deletions
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10
src/common/x64/native_clock.cpp
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@ -55,8 +55,9 @@ 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());
do {
current_time_point.pack = Common::AtomicLoad128(time_point.pack.data());
_mm_mfence();
const u64 current_measure = __rdtsc();
u64 diff = current_measure - current_time_point.inner.last_measure;
@ -66,7 +67,7 @@ u64 NativeClock::GetRTSC() {
: 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, current_time_point.pack));
/// The clock cannot be more precise than the guest timer, remove the lower bits
return new_time_point.inner.accumulated_ticks & inaccuracy_mask;
}
@ -75,13 +76,14 @@ 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());
do {
current_time_point.pack = Common::AtomicLoad128(time_point.pack.data());
new_time_point.pack = current_time_point.pack;
_mm_mfence();
new_time_point.inner.last_measure = __rdtsc();
} while (!Common::AtomicCompareAndSwap(time_point.pack.data(), new_time_point.pack,
current_time_point.pack));
current_time_point.pack, current_time_point.pack));
}
}