cpc_event

- data structure to describe CPU performance counters

Synopsis

#include <libcpc.h>

Description

The libcpc interfaces manipulate CPU performance counters using the cpc_event_t data structure. This structure contains several fields that are common to all processors, and some that are processor-dependent. These structures can be declared by a consumer of the API, thus the size and offsets of the fields and the entire data structure are fixed per processor for any particular version of the library. See cpc_version(3CPC) for details of library versioning.

SPARC

For UltraSPARC, the structure contains the following members:

typedef struct {
        int ce_cpuver;
        hrtime_t ce_hrt;
        uint64_t ce_tick;
        uint64_t ce_pic[2];
        uint64_t ce_pcr;
} cpc_event_t;

x86

For Pentium, the structure contains the following members:

typedef struct {
        int ce_cpuver;
        hrtime_t ce_hrt;
        uint64_t ce_tsc;
        uint64_t ce_pic[2];
        uint32_t ce_pes[2];
#define ce_cesr ce_pes[0]
} cpc_event_t;

The APIs are used to manipulate the highly processor-dependent control registers (the ce_pcr, ce_cesr, and ce_pes fields); the programmer is strongly advised not to reference those fields directly in portable code. The ce_pic array elements contain 64-bit accumulated counter values. The hardware registers are virtualized to 64-bit quantities even though the underlying hardware only supports 32-bits (UltraSPARC) or 40-bits (Pentium) before overflow.

The ce_hrt field is a high resolution timestamp taken at the time the counters were sampled by the kernel. This uses the same timebase as gethrtime(3C).

On SPARC V9 machines, the number of cycles spent running on the processor is computed from samples of the processor-dependent %tick register, and placed in the ce_tick field. On Pentium processors, the processor-dependent time-stamp counter register is similarly sampled and placed in the ce_tsc field.

Attributes

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

See Also

gethrtime(3C), cpc(3CPC), cpc_version(3CPC), libcpc(3LIB), attributes(5)