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| CPU Performance Counters Library Functions | cpc_count_usr_events(3CPC) |
| | cpc_count_usr_events, cpc_count_sys_events - enable and disable performance counters |
SYNOPSIS
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cc [ flag... ] file... -lcpc [ library... ]
#include <libcpc.h> int cpc_count_usr_events(int enable); |
| | int cpc_count_sys_events(int enable); |
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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_count_usr_events() function can be used to control whether events are counted on
behalf of the application running in user mode, while cpc_count_sys_events() can be used to control whether events are counted on behalf
of the application while it is running in the kernel, without otherwise
disturbing the binding of events to the invoking LWP. If the enable argument is non-zero, counting of events is enabled,
otherwise they are disabled.
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Upon successful completion, cpc_count_usr_events()
and cpc_count_sys_events() return 0.
Otherwise, the functions return -1 and set errno to indicate the error.
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The cpc_count_usr_events() and cpc_count_sys_events() functions will fail if:
-
EAGAIN
- The associated performance counter
context has been invalidated by another process.
-
EINVAL
- No performance counter context has been created, or an attempt was made
to enable system events while delivering counter overflow signals.
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| | Example 1. Use cpc_count_usr_events
to minimize code needed by application.
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In this example, the routine cpc_count_usr_events()
is 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 interfaces 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.
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int have_counters = 0;
int
main(int argc, char *argv[])
{
if (cpc_version(CPC_VER_CURRENT) == CPC_VER_CURRENT &&
cpc_getcpuver() != -1 && cpc_access() == 0)
have_counters = 1;
/* ... other application code */
if (have_counters)
(void) cpc_count_usr_events(1);
/* ==> Code to be measured goes here <== */
if (have_counters)
(void) cpc_count_usr_events(0);
/* ... other application code */
}
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See attributes(5)
for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
| Availability | SUNWcpcu (32-bit) |
| | SUNWcpcux (64-bit) |
| Interface Stability | Evolving |
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