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PERFMONCTL(2) Linux Programmer's Manual PERFMONCTL(2)


perfmonctl - interface to IA-64 performance monitoring unit


#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.


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:

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.
perfmonctl(int fd, PFM_WRITE_PMCS, pfarg_reg_t *pmcs, n);
Set PMC registers.
perfmonctl(int fd, PFM_WRITE_PMDS, pfarg_reg_t *pmds, n);
Set PMD registers.
perfmonctl(int fd, PFM_READ_PMDS, pfarg_reg_t *pmds, n);
Read PMD registers.
perfmonctl(int fd, PFM_START, NULL, 0);
Start monitoring.
perfmonctl(int fd, PFM_STOP, NULL, 0);
Stop monitoring.
perfmonctl(int fd, PFM_LOAD_CONTEXT, pfarg_load_t *largs, 1);
Attach the context to a thread.
perfmonctl(int fd, PFM_UNLOAD_CONTEXT, NULL, 0);
Detach the context from a thread.
perfmonctl(int fd, PFM_RESTART, NULL, 0);
Restart monitoring after receiving an overflow notification.
perfmonctl(int fd, PFM_GET_FEATURES, pfarg_features_t *arg, 1);
perfmonctl(int fd, PFM_DEBUG, val, 0);
If val is nonzero, enable debugging mode, otherwise disable.
perfmonctl(int fd, PFM_GET_PMC_RESET_VAL, pfarg_reg_t *req, n);
Reset PMC registers to default values.


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


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


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


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).



The perfmon2 interface specification


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2021-03-22 Linux