2 files changed, 46 insertions, 10 deletions

diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index 8b08332ab..76c66e7ee 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -6,6 +6,7 @@
 #include <thread>
 
 #include "common/atomic_ops.h"
+#include "common/steady_clock.h"
 #include "common/uint128.h"
 #include "common/x64/native_clock.h"
 
@@ -39,6 +40,12 @@ static u64 FencedRDTSC() {
 }
 #endif
 
+template <u64 Nearest>
+static u64 RoundToNearest(u64 value) {
+    const auto mod = value % Nearest;
+    return mod >= (Nearest / 2) ? (value - mod + Nearest) : (value - mod);
+}
+
 u64 EstimateRDTSCFrequency() {
     // Discard the first result measuring the rdtsc.
     FencedRDTSC();
@@ -46,18 +53,18 @@ u64 EstimateRDTSCFrequency() {
     FencedRDTSC();
 
     // Get the current time.
-    const auto start_time = std::chrono::steady_clock::now();
+    const auto start_time = Common::RealTimeClock::Now();
     const u64 tsc_start = FencedRDTSC();
-    // Wait for 200 milliseconds.
-    std::this_thread::sleep_for(std::chrono::milliseconds{200});
-    const auto end_time = std::chrono::steady_clock::now();
+    // Wait for 250 milliseconds.
+    std::this_thread::sleep_for(std::chrono::milliseconds{250});
+    const auto end_time = Common::RealTimeClock::Now();
     const u64 tsc_end = FencedRDTSC();
     // Calculate differences.
     const u64 timer_diff = static_cast<u64>(
         std::chrono::duration_cast<std::chrono::nanoseconds>(end_time - start_time).count());
     const u64 tsc_diff = tsc_end - tsc_start;
     const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, timer_diff);
-    return tsc_freq;
+    return RoundToNearest<1000>(tsc_freq);
 }
 
 namespace X64 {
@@ -65,13 +72,29 @@ 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_} {
+    // Thread to re-adjust the RDTSC frequency after 10 seconds has elapsed.
+    time_sync_thread = std::jthread{[this](std::stop_token token) {
+        // Get the current time.
+        const auto start_time = Common::RealTimeClock::Now();
+        const u64 tsc_start = FencedRDTSC();
+        // Wait for 10 seconds.
+        if (!Common::StoppableTimedWait(token, std::chrono::seconds{10})) {
+            return;
+        }
+        const auto end_time = Common::RealTimeClock::Now();
+        const u64 tsc_end = FencedRDTSC();
+        // Calculate differences.
+        const u64 timer_diff = static_cast<u64>(
+            std::chrono::duration_cast<std::chrono::nanoseconds>(end_time - start_time).count());
+        const u64 tsc_diff = tsc_end - tsc_start;
+        const u64 tsc_freq = MultiplyAndDivide64(tsc_diff, 1000000000ULL, timer_diff);
+        rtsc_frequency = tsc_freq;
+        CalculateAndSetFactors();
+    }};
+
     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);
-    clock_rtsc_factor = GetFixedPoint64Factor(emulated_clock_frequency, rtsc_frequency);
-    cpu_rtsc_factor = GetFixedPoint64Factor(emulated_cpu_frequency, rtsc_frequency);
+    CalculateAndSetFactors();
 }
 
 u64 NativeClock::GetRTSC() {
@@ -131,6 +154,14 @@ u64 NativeClock::GetCPUCycles() {
     return MultiplyHigh(rtsc_value, cpu_rtsc_factor);
 }
 
+void NativeClock::CalculateAndSetFactors() {
+    ns_rtsc_factor = GetFixedPoint64Factor(NS_RATIO, rtsc_frequency);
+    us_rtsc_factor = GetFixedPoint64Factor(US_RATIO, rtsc_frequency);
+    ms_rtsc_factor = GetFixedPoint64Factor(MS_RATIO, rtsc_frequency);
+    clock_rtsc_factor = GetFixedPoint64Factor(emulated_clock_frequency, rtsc_frequency);
+    cpu_rtsc_factor = GetFixedPoint64Factor(emulated_cpu_frequency, rtsc_frequency);
+}
+
 } // namespace X64
 
 } // namespace Common
diff --git a/src/common/x64/native_clock.h b/src/common/x64/native_clock.h
index 38ae7a462..03ca291d8 100644
--- a/src/common/x64/native_clock.h
+++ b/src/common/x64/native_clock.h
@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include "common/polyfill_thread.h"
 #include "common/wall_clock.h"
 
 namespace Common {
@@ -28,6 +29,8 @@ public:
 private:
     u64 GetRTSC();
 
+    void CalculateAndSetFactors();
+
     union alignas(16) TimePoint {
         TimePoint() : pack{} {}
         u128 pack{};
@@ -47,6 +50,8 @@ private:
     u64 ms_rtsc_factor{};
 
     u64 rtsc_frequency;
+
+    std::jthread time_sync_thread;
 };
 } // namespace X64