From 979e53b87b5288c582392beff618da978ca4152c Mon Sep 17 00:00:00 2001
From: merry <git@mary.rs>
Date: Sat, 2 Apr 2022 21:05:49 +0100
Subject: [PATCH] native_clock: Use writeback from CAS to avoid double-loading
---
src/common/x64/native_clock.cpp | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index 2a2664e5d5..7a3f21dcf1 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -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));
}
}