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
occurred since an unspecified time in the past (perhaps system boot,
perhaps program startup).
Accessing true cycle counters can be difficult on some CPUs and operat-
ing systems. cpucycles() does its best to produce accurate results,
but selects a low-precision counter if the only other option is fail-
ure.
cpucycles_persecond() returns an estimate for the number of CPU cycles
per second. This estimate comes from /etc/cpucyclespersecond if that
file exists, otherwise from various OS mechanisms, otherwise from the
cpucyclespersecond environment variable if that is set, otherwise
2399987654.
cpucycles_implementation() returns the name of the counter in use:
e.g., "amd64-pmc".
cpucycles_version() returns the libcpucycles version number as a
string: e.g., "20240318". Results of cpucycles_implementation() should
be interpreted relative to cpucycles_version().
cpucycles is actually a function pointer. The first call to cpucy-
cles() or cpucycles_persecond() or cpucycles_implementation() selects
one of the available counters and updates the cpucycles pointer accord-
ingly. Subsequent calls to cpucycles() are thread-safe.
SEE ALSO
gettimeofday(2), clock_gettime(2)
cpucycles(3)
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