How can I check the last 5 min overall cpu usage using SAR

Question

I know this example of sar sar -u 1 3 which gives statistics for the next 3 seconds with 1 second interval .

However sar also keeps on collecting the information in background (My cron set to collect stats for every minute ) . Is there any way I can simply query using sar command to tell the last 5 mins statistics and its average .

Right now I am using following below command

interval=5; sar -f /var/log/sysstat/sa22 | tail -n $interval | head -n -1 | awk '{print $4+$6}'| awk  '{s+=$1} END {print s/$interval}' 

to check the overall cpu usage in last 5 min .

Is there a better way ?

Answer 1

Unfortunately when using the -f option in sar together with interval and count it doesn't return the average value for the given interval (as you would expect). Instead it always returns the first recorded value in the sar file

The only way to work around that is to use the -s option which allows you to specify a time at which to start your sampling period. I've provided a perl script below that finishes with a call to sar that is constructed in a way that will return what you're looking for.

Hope this helps.

Peter Rhodes.

#!/usr/bin/perl

$interval = 300;        # seconds.
$epoch    = `date +%s`;
$epoch   -= $interval;
$time     = `date -d \@$epoch +%H:%M:00`;
$dom      = `date +%d`;
chomp($time,$dom);
system("sar -f /var/log/sysstat/sa$dom -B -s $time 300 1");