perfmonctl(2)                 System Calls Manual                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 HISTORY.

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.

STANDARDS
       Linux on IA-64.

HISTORY
       Added in Linux 2.4; removed in Linux 5.10.

       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

Linux man-pages 6.7               2023-10-31                     perfmonctl(2)