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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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5
libc/testlib/ezbenchreport.c
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@ -19,6 +19,7 @@
#include "libc/fmt/fmt.h"
#include "libc/math.h"
#include "libc/runtime/gc.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/stdio.h"
#include "libc/testlib/testlib.h"
#include "libc/time/time.h"
@ -28,10 +29,11 @@ STATIC_YOINK("strnwidth");
void __testlib_ezbenchreport(const char *form, uint64_t c1, uint64_t c2) {
uint64_t ns1, ns2;
__warn_if_powersave();
ns1 = rintl(ConvertTicksToNanos(c1));
ns2 = rintl(ConvertTicksToNanos(c2));
(fprintf)(stderr,
VEIL("r", " * %-19s l: %,9lu𝑐 %,9lu𝑛𝑠 m: %,9lu𝑐 %,9lu𝑛𝑠\n"),
VEIL("r", " * %-19s l: %,9luc %,9luns m: %,9luc %,9luns\n"),
form, c1, ns1, c2, ns2);
}
@ -39,6 +41,7 @@ void __testlib_ezbenchreport_n(const char *form, char z, size_t n, uint64_t c) {
char msg[128];
uint64_t bps;
long double cn, lat;
__warn_if_powersave();
(snprintf)(msg, sizeof(msg), "%s %c=%d", form, z, n);
cn = ConvertTicksToNanos(c);
if (!n) {