man pages section 3: Extended Library Functions, Volume 1

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Updated: July 2014
 
 

cpc_disable(3CPC)

Name

cpc_enable, cpc_disable - enable and disable performance counters and hardware sampling

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 and hardware sampling 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 and hardware sampling 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
Committed
MT-Level
Safe

See Also

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