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utils/sysinfo.cpp: Yield CPU time when measuring TSC freq

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Elad 2024-10-30 08:36:40 +02:00
parent 8b8396b945
commit edfe940543
1 changed files with 20 additions and 3 deletions
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23
rpcs3/util/sysinfo.cpp
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@ -22,6 +22,8 @@
#endif #endif
#endif #endif
#include <thread>
#include "util/asm.hpp" #include "util/asm.hpp"
#include "util/fence.hpp" #include "util/fence.hpp"
@ -785,7 +787,7 @@ static const bool s_tsc_freq_evaluated = []() -> bool
constexpr ullong timer_freq = 1'000'000'000; constexpr ullong timer_freq = 1'000'000'000;
#endif #endif
constexpr u64 retry_count = 1000; constexpr u64 retry_count = 1024;
// First is entry is for the onset measurements, last is for the end measurements // First is entry is for the onset measurements, last is for the end measurements
constexpr usz sample_count = 2; constexpr usz sample_count = 2;
@ -803,7 +805,7 @@ static const bool s_tsc_freq_evaluated = []() -> bool
const ullong sec_base = ts0.tv_sec; const ullong sec_base = ts0.tv_sec;
#endif #endif
constexpr usz sleep_time_ms = 20; constexpr usz sleep_time_ms = 40;
for (usz sample = 0; sample < sample_count; sample++) for (usz sample = 0; sample < sample_count; sample++)
{ {
@ -832,10 +834,25 @@ static const bool s_tsc_freq_evaluated = []() -> bool
rdtsc_diff[sample] = rdtsc_read2 >= rdtsc_read ? rdtsc_read2 - rdtsc_read : u64{umax}; rdtsc_diff[sample] = rdtsc_read2 >= rdtsc_read ? rdtsc_read2 - rdtsc_read : u64{umax};
} }
if (rdtsc_read2 - rdtsc_read < std::min<usz>(i, 300) && rdtsc_read2 >= rdtsc_read) // 80 results in an error range of 4000 hertz (0.00025% of 4GHz CPU, quite acceptable)
// Error of 2.5 seconds per month
if (rdtsc_read2 - rdtsc_read < 80 && rdtsc_read2 >= rdtsc_read)
{ {
break; break;
} }
// 8 yields seems to reduce significantly thread contention, improving accuracy
// Even 3 seem to do the job though, but just in case
if (i % 128 == 64)
{
std::this_thread::yield();
}
// Take 50% more yields with the last sample because it helps accuracy additionally the more time that passes
if (sample == sample_count - 1 && i % 256 == 128)
{
std::this_thread::yield();
}
} }
if (sample < sample_count - 1) if (sample < sample_count - 1)