perfstat_cpu_util Subroutine
Purpose
Calculates central processing unit utilization.
Library
perfstat library (libperfstat.a)
Syntax
#include <libperfstat.h>int perfstat_cpu_util (cpustats, userbuff, sizeof_userbuff, desired_number)
perfstat_rawdata_t * cpustats;
perfstat_cpu_util_t * userbuff;
int sizeof_userbuff ;
int desired_number ;Description
The perfstat_cpu_util subroutine calculates the CPU utilization-related metrics for the current and the previous values passed to the perfstat_rawdata_t data structure. Both the system utilization and the per CPU utilization values can be obtained, using the same API, by mentioning the type field of the perfstat_rawdata_t data structure as UTIL_CPU_TOTAL or UTIL_CPU. The UTIL_CPU_TOTAL and UTIL_CPU are the macros, which can be referred to in the definition of the perfstat_rawdata_t data structure. If the attributes name and userbuff are set to NULL, and the sizeof_userbuff parameter is set to zero, the size of the current version of the perfstat_cpu_util_t structure is returned. If the desired_elements parameter is set to zero, the number of current elements, from the cpustats parameter, are returned.
Parameters
| Item | Description |
|---|---|
| cpustats | Calculates the utilization-related metrics from the current and the previous values. The cpustats parameter is of the type perfstat_rawdata_t. The curstat and the prevstat attributes, points to the perfstat_cpu_util_t data structure. Note: To calculate the partition level CPU utilization,
set the cpustats parameter to UTIL_CPU_TOTAL . For the
individual CPU utilization, set the cpustats parameter to UTIL_CPU.
The ID of the individual CPU can also be specified in the cpustats parameter
if utilization to be calculated applies only to a specific CPU.
|
| userbuff | Specifies the memory area that is to be filled with one or more perfstat_cpu_util_t structures. |
| sizeof_userbuff | Specifies the size of the perfstat_cpu_util_t structure. Note: To
obtain the size of the latest version of perfstat_cpu_util_t structure,
set the sizeof_userbuff parameter to 0, and set the name and userbuff parameters
to NULL.
|
| desired_number | Specifies the number of perfstat_cpu_util_t structures to copy to the userbuff parameter. |
Return Values
Unless the perfstat_cpu_util subroutine is used to retrieve the number of available structures, the number of structures filled is returned upon successful completion. If unsuccessful, a value of -1 is returned and the errno global variable is set.
Error Codes
The perfstat_cpu_util subroutine is unsuccessful if the following is true:
| Item | Description |
|---|---|
| EINVAL | One of the parameters is not valid. |
Files
The libperfstat.h file defines standard macros, data types, and subroutines.