PERFMONCTL

Section: Linux System Calls (2)
Updated: 28 August 2006
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NAME

perfmonctl - interface to PMU  

SYNOPSIS

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

long perfmonctl(int fd, int cmd, void *arg, int narg);
 

DESCRIPTION

perfmonctl system call provides an interface to PMU (performance monitoring unit). PMU consists of PMD (performance monitoring data) registers and PMC (performance monitoring control) registers, where are gathered the hardware statistic.

perfmonctl will apply a function cmd to input arguments arg. The number of arguments is defined by input variable narg. fd specifies the perfmon context to operate on.

The implemented commands cmd are:

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

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

The file descriptor, apart from passing it to perfmonctl, can be used to read event notifications (type pfm_msg_t) using the read(2) system call. Both select(2) and poll(2) can be used to wait for event notifications.

The context can be destroyed using the close(2) system call.

PFM_WRITE_PMCS
set PMC registers
perfmonctl(int fd, PFM_WRITE_PMCS , pfarg_pmc_t *pmcs, n);
PFM_WRITE_PMDS        
set PMD registers
perfmonctl(int fd, PFM_WRITE_PMDS , pfarg_pmd_t *pmds, n);
PFM_READ_PMDS  
read PMD registers
perfmonctl(int fd, PFM_READ_PMDS , pfarg_pmd_t *pmds, n);
PFM_START      
start monitoring
perfmonctl(int fd, PFM_START , arg , 1);
perfmonctl(int fd, PFM_START , NULL , 0);
PFM_STOP       
stop monitoring
perfmonctl(int fd, PFM_START , NULL , 0);
PFM_LOAD_CONTEXT       
attach the context to a thread
perfmonctl(int fd, PFM_LOAD_CONTEXT ,pfarg_load_t *largs,1);
PFM_UNLOAD_CONTEXT     
detach the context from a thread
perfmonctl(int fd, PFM_UNLOAD_CONTEXT , NULL , 0);
PFM_RESTART    
restart monitoring after recieving an overflow notification
perfmonctl(int fd, PFM_RESTART , NULL , 0);
PFM_CREATE_EVTSETS     
create or modify event sets
perfmonctl(int fd, PFM_CREATE_EVTSETS, pfarg_setdesc_t *desc , n);
PFM_DELETE_EVTSETS     
delete event sets
perfmonctl(int fd, PFM_DELETE_EVTSET, pfarg_setdesc_t *desc , n);
PFM_GETINFO_EVTSETS    
get information about event sets
perfmonctl(int fd, PFM_GETINFO_EVTSETS, pfarg_setinfo_t *info, n);

 

RETURN VALUE

performctl returns zero when the operation is successful. On error -1 is returned and an error code is set in errno.

 

AVAILABILITY

This syscall is implemented only on the IA-64 architecture since kernel 2.6.

 

SEE ALSO

gprof(1), The perfmon2 interface specification


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
AVAILABILITY
SEE ALSO

linux.jgfs.net manual pages