FreeBSD Manual Pages
cpucycles(3) cpucycles(3)
NAME
cpucycles - count CPU cycles
SYNOPSIS
#include <cpucycles.h>
long long count = cpucycles();
long long persecond = cpucycles_persecond();
const char *implementation = cpucycles_implementation();
const char *version = cpucycles_version();
Link with -lcpucycles. Old systems may also need -lrt.
DESCRIPTION
cpucycles() returns an estimate for the number of CPU cycles that have oc-
curred since an unspecified time in the past (perhaps system boot, perhaps
program startup).
Accessing true cycle counters can be difficult on some CPUs and operating
systems. cpucycles() does its best to produce accurate results, but se-
lects a low-precision counter if the only other option is failure.
cpucycles_persecond() returns an estimate for the number of CPU cycles per
second. This estimate comes from /etc/cpucyclespersecond if that file ex-
ists, otherwise from various OS mechanisms, otherwise from the cpucycles-
persecond environment variable if that is set, otherwise 2399987654.
cpucycles_implementation() returns the name of the counter in use: e.g.,
"amd64-perfpmc".
cpucycles_version() returns the libcpucycles version number as a string:
e.g., "20260625". Results of cpucycles_implementation() should be inter-
preted relative to cpucycles_version().
cpucycles is actually a function pointer. The first call to cpucycles() or
cpucycles_persecond() or cpucycles_implementation() selects one of the
available counters and updates the cpucycles pointer accordingly. Subse-
quent calls to cpucycles() are thread-safe.
SEE ALSO
gettimeofday(2), clock_gettime(2)
cpucycles(3)
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