sar


sar -u

%usr
identical to vmstat

%sys
identical to vmstat

%wio
percentage of time the CPU was idle waiting for I/O. Useful in identifying whether the system is I/O bound.

%idle
percentage of time CPU had nothing to do or was waiting for the network. total CPU idle percentage is sum of %wio and %idle.


 

sar -b

lread/s
User read requests

bread/s
I/O to disk

%rcache
Ratio of bread/s to lread/s. Zero is worst case. Should be above 80%


 

sar -c

scall/s
Rate of all system calls per second

fork/s
Forks per second

exec/s
Execs per second


 

sar -d


Run with interval of 30-60 seconds

avque
Average number of requests in the disk queue while the drive was busy.

%busy
percentage of time device was busy servicing a request. Important because it shows how saturated a disk drive is. You should strive to keep %busy below 25% for optimal system performance.

avwait
Average amount of time a request was waiting on the queue

avserv
Average amount of time it takes a drive to process a request. If avwait plus avserv exceeds 50 milliseconds, the drive is running too slow for good response time.

r+w/s
Number of transfers per second

blks/s
Amount of data transferred to and from the disk drive. 512-byte blocks.


 

sar -g

pgout/s
Number of times the pageout daemon was activated to free memory.

ppgout/s
Number of pages that had to be written out to the swap space to free memory.

pgfree/s
Total number of pages freed per second by the pageout daemon or the swapper

pgscan/s
Number of pages examined by the pageout daemon to see if they can be freed and is identical to sr in vmstat. If pgscan is nonzero, the pageout daemon is running looking for pages to free. Note that this does not necessarily mean that there is a memory shortage if your system has paged buffer cache.

%ufsipf/s
Key piece of info and indicates how often the kernel had to resue an inactive inode that had pages associated with it in the buffer cache. This is usually an indication of an inode table that is too small causing useful buffer cache data to be thrown away. Should be zero.


 

sar -w

pswot/s
pages swapped out. You should not see any swapping activity in the output of sar -w. Otherwise, this indicates a severe memory shortage.

pswin/s
pages swapped in


 

sar -q

runq-sz
Run queue size. high values (greater than 4) mean the system is very CPU-bound.

swpq-sz
Number of swapped out processes. Should always be zero.