CPC_ENABLE(3CPC) CPU Performance Counters Library Functions CPC_ENABLE(3CPC)


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


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Evolving |
+--------------------+-----------------+
|MT-Level | Safe |
+--------------------+-----------------+

SEE ALSO


cputrack(1), cpc(3CPC), cpc_open(3CPC), libcpc(3LIB), attributes(5)


January 31, 2005 CPC_ENABLE(3CPC)