I386_PMC_INFO(2) (i386)

I386_PMC_INFO(2) | System Calls Manual (i386) | I386_PMC_INFO(2)

# NAME

i386_pmc_info, i386_pmc_startstop, i386_pmc_read — interface to CPU performance counters

# LIBRARY

i386 Architecture Library (libi386, -li386)

# SYNOPSIS

#include <sys/types.h>
#include <machine/sysarch.h>
#include <machine/specialreg.h>
int
i386_pmc_info(struct i386_pmc_info_args *ia);
int
i386_pmc_startstop(struct i386_pmc_startstop_args *ssa);
int
i386_pmc_read(struct i386_pmc_read_args *ra);

# DESCRIPTION

These functions provide an interface to the CPU performance counters on the 586-class and 686-class processors.
i386_pmc_info() will return information about the available CPU counters. The information is returned in ia having the following structure:

    struct i386_pmc_info_args {
            int     type;
            int     flags;
    };

The type member describes the class of performance counters available. Valid values are:

PMC_TYPE_NONE
  No PMC support
PMC_TYPE_I586
  586-class CPUs
PMC_TYPE_I686
  686-class Intel CPUs
PMC_TYPE_K7
  686-class AMD CPUs

The flags member describes additional capabilities of the processor. Valid values are:

PMC_INFO_HASTSC
  CPU has time-stamp counter

i386_pmc_startstop() is used to start and stop the measurement of the CPU performance counters. The argument ssa has the following structure:

    struct i386_pmc_startstop_args {
            int counter;
            uint64_t val;
            uint8_t event;
            uint8_t unit;
            uint8_t compare;
            uint8_t flags;
    };

The counter specified by the member counter is started if the member flags has PMC_SETUP_KERNEL or PMC_SETUP_USER set, otherwise the counter is stopped. The initial value of the counter is set to val. Additional values for the flags member are PMC_SETUP_EDGE and PMC_SETUP_INV. The event member specifies some event written to the control register. The unit member specifies the measurement units. The compare member is a mask for the counter.
i386_pmc_read() will return information about a specific CPU counter measured during the last measurement period determined by the calling of i386_pmc_startstop(). The information is returned in ra having the following structure:

    struct i386_pmc_read_args {
            int counter;
            uint64_t val;
            uint64_t time;
    };

The counter to read should be specified by the counter member. Counters are numbered from 0 to `PMC_NCOUNTERS`. The value of the counter is returned in the val member. The time since epoch, measured in CPU clock cycles, is returned in the time member.

# RETURN VALUES

Upon successful completion zero is returned, otherwise -1 is returned on failure.

November 10, 2001 | NetBSD 8.3