Access to CPU performance counters is possible only on systems where the appropriate hardware exists and is correctly configured. The cpc_access() function must be used to determine if the hardware exists and is accessible on the platform before any of the interfaces that use the counters are invoked.

When the hardware is available, access to the per-process counters is always allowed to the process itself, and allowed to other processes mediated using the existing security mechanisms of /proc.

Upon successful completion, cpc_access() returns 0. Otherwise, it returns -1 and sets errno to indicate the error.

By default, two common errno values are decoded and cause the library to print an error message using its reporting mechanism. See cpc_seterrfn(3CPC) for a description of how this behavior can be modified.

The cpc_access() function will fail if:

EAGAIN

Another process may be sampling system-wide CPU statistics.

ENOSYS

CPU performance counters are inaccessible on this machine. This error can occur when the machine supports CPU performance counters, but some software components are missing. Check to see that all CPU Performance Counter packages have been correctly installed.

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

cpc(3CPC), cpc_seterrfn(3CPC), proc(4), attributes(5)