Tribblix: manual page: cpc

CPC_ENABLE(3CPC) CPU Performance Counters Library Functions

NAME

cpc_enable, cpc_disable - enable and disable performance counters

SYNOPSIS

cc [ flag... ] file... -lcpc [ library... ]
#include <libcpc.h>

int cpc_enable(cpc_t *cpc);

int cpc_disable(cpc_t *cpc);

DESCRIPTION

In certain applications, it can be useful to explicitly enable and
disable performance counters at different times so that the
performance of a critical algorithm can be examined. The cpc_enable()
and cpc_disable() functions can be used to enable and disable the
performance counters without otherwise disturbing the invoking LWP's
performance hardware configuration.

RETURN VALUES

Upon successful completion, cpc_enable() and cpc_disable() return 0.
Otherwise, they return -1 and set errno to indicate the error.

ERRORS

These functions will fail if:

EAGAIN
The associated performance counter context has been
invalidated by another process.

EINVAL
No performance counter context has been created for the
calling LWP.

EXAMPLES

Example 1: Use cpc_enable and cpc_disable to minimize code needed by

application.

In the following example, the cpc_enable() and cpc_disable()
functions are used to minimize the amount of code that needs to be
added to the application. The cputrack(1) command can be used in
conjunction with these functions to provide event programming,
sampling, and reporting facilities.

If the application is instrumented in this way and then started by
cputrack with the nouser flag set in the event specification,
counting of user events will only be enabled around the critical code
section of interest. If the program is run normally, no harm will
ensue.

int
main(int argc, char *argv[])
{
cpc_t *cpc = cpc_open(CPC_VER_CURRENT);
/* ... application code ... */

if (cpc != NULL)
(void) cpc_enable(cpc);

/* ==> Code to be measured goes here <== */

if (cpc != NULL)
(void) cpc_disable(cpc);

/* ... other application code */
}

ATTRIBUTES