Other Alias
sg_get_disk_io_stats_diffSYNOPSIS
#include <statgrab.h>
sg_disk_io_stats *sg_get_disk_io_stats(int *entries);
sg_disk_io_stats *sg_get_disk_io_stats_diff(int *entries);
DESCRIPTION
Both calls take a pointer to an int, entries, which is filled with the number of disks the machine has. This is needed to know how many sg_disk_io_stats structures have been returned. A pointer is returned to the first sg_disk_io_stats.sg_get_disk_io_stats returns the disk IO stored in the kernel which holds the amount of data transferred since bootup. On some platforms, such as Solaris 7, this value is stored in a 32bit int, so wraps around when it reaches 4GB. Other platforms, such as Solaris 8, hold the value in a 64bit int, which wraps somewhere near 17 million terabytes.
sg_get_disk_io_stats_diff is the same as sg_get_disk_io_stats except it will return the difference since the last call. So, for instance a call to sg_get_disk_io_stats_diff is made, and called again 5 seconds later. Over that time, 2000 bytes of traffic were written and 10000 bytes read. write_bytes will store 2000 bytes, read_bytes will store 10000, and systime will store 5. This function copes with wrap arounds by the O/S so should be seemless to use.
On Solaris libstatgrab will attempt to get the cXtXdXsX representation for the disk_name string. If it fails it will use a name like sd0. On some systems programs calling libstatgrab will need elevated privileges to lookup some of the names. The mappings are built up when sg_init is called.
RETURN VALUES
All diskio statistics return a pointer to a structure of type sg_disk_io_stats.
typedef struct{
char *disk_name;
long long read_bytes;
long long write_bytes;
time_t systime;
}sg_disk_io_stats;
- disk_name
- The name known to the operating system. (eg. on linux it might be hda)
- read_bytes
- The number of bytes the disk has read.
- write_bytes
- The number of bytes the disk has written.
- systime
- The time period over which read_bytes and write_bytes were transferred.
BUGS
On the very first call sg_get_disk_io_stats_diff will return the same as sg_get_disk_io_stats. After the first call it will always return the difference.On operating systems that hold only 32bits of data there is a problem if the values wrap twice. For example, on Solaris 7 if 9GB is transferred and the operating system wraps at 4GB, the sg_get_disk_io_stats_diff function will return 5GB.