perfmonctl(2)

NAME
perfmonctl - interface to IA-64 performance monitoring unit

SYNOPSIS
#include <syscall.h>
#include <perfmon.h>

long perfmonctl(int fd, int cmd, void arg[.narg], int narg);

Note: There is no glibc wrapper for this system call; see NOTES.

DESCRIPTION
The IA-64-specific perfmonctl() system call provides an interface to the PMU (performance monitoring unit). The PMU consists of PMD (performance monitoring data) registers and PMC (performance monitoring control) registers, which gather hardware statistics.

perfmonctl() applies the operation cmd to the input arguments specified by arg. The number of arguments is defined by narg. The fd argument specifies the perfmon context to operate on.

Supported values for cmd are:

PFM_CREATE_CONTEXT
    perfmonctl(int fd, PFM_CREATE_CONTEXT, pfarg_context_t *ctxt, 1);
    Set up a context.

    The fd parameter is ignored. A new perfmon context is created as specified in ctxt and its file descriptor is returned in ctxt->ctx_fd.

    The file descriptor can be used in subsequent calls to perfmonctl() and can be used to read event notifications (type pfm_msg_t) using read(2). The file descriptor is pollable using select(2), poll(2), and epoll(7).

    The context can be destroyed by calling close(2) on the file descriptor.

PFM_WRITE_PMCS
    perfmonctl(int fd, PFM_WRITE_PMCS, pfarg_reg_t *pmcs, n);
    Set PMC registers.

PFM_WRITE_PMDS
    perfmonctl(int fd, PFM_WRITE_PMDS, pfarg_reg_t *pmds, n);
    Set PMD registers.

PFM_READ_PMDS
    perfmonctl(int fd, PFM_READ_PMDS, pfarg_reg_t *pmds, n);
    Read PMD registers.

PFM_START
    perfmonctl(int fd, PFM_START, NULL, 0);
    Start monitoring.

PFM_STOP
    perfmonctl(int fd, PFM_STOP, NULL, 0);
    Stop monitoring.

PFM_LOAD_CONTEXT
    perfmonctl(int fd, PFM_LOAD_CONTEXT, pfarg_load_t *largs, 1);
    Attach the context to a thread.

PFM_UNLOAD_CONTEXT
    perfmonctl(int fd, PFM_UNLOAD_CONTEXT, NULL, 0);
    Detach the context from a thread.

PFM_RESTART
    perfmonctl(int fd, PFM_RESTART, NULL, 0);
    Restart monitoring after receiving an overflow notification.

PFM_GET_FEATURES
    perfmonctl(int fd, PFM_GET_FEATURES, pfarg_features_t *arg, 1);

PFM_DEBUG
    perfmonctl(int fd, PFM_DEBUG, val, 0);
    If val is nonzero, enable debugging mode, otherwise disable.

PFM_GET_PMC_RESET_VAL
    perfmonctl(int fd, PFM_GET_PMC_RESET_VAL, pfarg_reg_t *req, n);
    Reset PMC registers to default values.

RETURN VALUE
perfmonctl() returns zero when the operation is successful. On error, -1 is returned and errno is set to indicate the error.

VERSIONS
perfmonctl() was added in Linux 2.4; it was removed in Linux 5.10.

STANDARDS
perfmonctl() is Linux-specific and is available only on the IA-64 architecture.

NOTES
This system call was broken for many years, and ultimately removed in Linux 5.10.

glibc does not provide a wrapper for this system call; on kernels where it exists, call it using syscall(2).

SEE ALSO
gprof(1)

The perfmon2 interface specification