perfstat_disk_total Subroutine

Purpose

Retrieves global disk usage statistics.

Library

Perfstat library (libperfstat.a)

Syntax

#include <libperfstat.h>

int perfstat_disk_total (name, userbuff, sizeof_struct, desired_number) perfstat_id_t *name; perfstat_disk_total_t *userbuff; size_t sizeof_struct; int desired_number;

Description

The perfstat_disk_total subroutine returns global disk usage statistics in a perfstat_disk_total_t structure.

To get statistics that are global to the whole system, the name parameter must be set to NULL, the userbuff parameter must be allocated, and the desired_number parameter must be set to 1.

The perfstat_disk_total subroutine retrieves information from the ODM database. This information is automatically cached into a dictionary which is assumed to be frozen once loaded. The perfstat_reset subroutine must be called to flush the dictionary whenever the machine configuration has changed.

To improve system performance, the collection of disk input and output statistics is disabled by default in current releases of AIX®.

To enable the collection of this data, run:

chdev -l sys0 -a iostat=true

To display the current setting, run:

lsattr -E -l sys0 -a iostat

Another way to enable the collection of the disk input and output statistics is to use the sys_parm API and the SYSP_V_IOSTRUN flag:

To get the current status of the flag, run the following:

struct vario var;
sys_parm(SYSP_GET,SYSP_V_IOSTRUN, &var);

To set the flag, run the following:

struct vario var;
var.v.v_iostrun.value=1; /* 1 to set & 0 to unset */
sys_parm(SYSP_SET,SYSP_V_IOSTRUN, &var);

Parameters

Item	Description
name	Must set to NULL.
userbuff	Points to the memory area that is to be filled with one or more perfstat_disk_total_t structures.
sizeof_struct	Specifies the size of the perfstat_disk_total_t structure: `sizeof(perfstat_disk_total_t)`
desired_number	Must set to 1.

Return Values

Upon successful completion, the number of structures that could be filled is returned. This is always 1. If unsuccessful, a value of -1 is returned and the errno global variable is set.

Error Codes

The perfstat_disk_total subroutine is unsuccessful if one of the following is true:

Item	Description
EINVAL	One of the parameters is not valid.
EFAULT	Insufficient memory.
ENOMEM	The string default length is too short.

Files

The libperfstat.h file defines standard macros, data types, and subroutines.