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Print warning when microbenchmarking w/ powersave

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RDTSC on Linux has so much jitter when the CPU is in powersave mode
causing things like microbenchmarks to have a 1000% margin of error
This commit is contained in:
Justine Tunney 2022-06-10 20:51:36 -07:00
parent 41c86fe86b
commit c6d8e516b2
5 changed files with 64 additions and 4 deletions
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19
test/libc/calls/clock_gettime_test.c
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@ -21,6 +21,7 @@
#include "libc/calls/struct/timespec.h"
#include "libc/calls/struct/timeval.h"
#include "libc/calls/syscall_support-sysv.internal.h"
#include "libc/dce.h"
#include "libc/nexgen32e/rdtsc.h"
#include "libc/runtime/runtime.h"
#include "libc/sysv/consts/auxv.h"
@ -49,7 +50,19 @@ BENCH(clock_gettime, bench) {
EZBENCH2("nowl", donothing, nowl());
EZBENCH2("rdtsc", donothing, rdtsc());
EZBENCH2("gettimeofday", donothing, gettimeofday(&tv, 0));
EZBENCH2("clock_gettime", donothing, clock_gettime(0, &ts));
EZBENCH2("__clock_gettime", donothing, __clock_gettime(0, &ts));
EZBENCH2("sys_clock_gettime", donothing, sys_clock_gettime(0, &ts));
EZBENCH2("clock_gettime 0", donothing, clock_gettime(0, &ts));
EZBENCH2("clock_gettime 1", donothing, clock_gettime(1, &ts));
EZBENCH2("clock_gettime 4", donothing, clock_gettime(4, &ts));
EZBENCH2("__clock_gettime 0", donothing, __clock_gettime(0, &ts));
EZBENCH2("__clock_gettime 1", donothing, __clock_gettime(1, &ts));
EZBENCH2("__clock_gettime 4", donothing, __clock_gettime(4, &ts));
if (IsWindows()) {
EZBENCH2("sys_clock_gettime 0", donothing, sys_clock_gettime_nt(0, &ts));
EZBENCH2("sys_clock_gettime 1", donothing, sys_clock_gettime_nt(1, &ts));
EZBENCH2("sys_clock_gettime 4", donothing, sys_clock_gettime_nt(4, &ts));
} else {
EZBENCH2("sys_clock_gettime 0", donothing, sys_clock_gettime(0, &ts));
EZBENCH2("sys_clock_gettime 1", donothing, sys_clock_gettime(1, &ts));
EZBENCH2("sys_clock_gettime 4", donothing, sys_clock_gettime(4, &ts));
}
}