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PERFMONCTL(2)                                                           Linux Programmer's 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, 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 perf‐
       mon 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.

CONFORMING TO
       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

Linux                                                                          2021-03-22                                                                  PERFMONCTL(2)