Load (computing): Difference between revisions

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Systems calculate the load ''average'' as the [[Moving average#Exponential moving average|exponentially damped/weighted moving average]] of the load ''number''. The three values of load average refer to the past one, five, and fifteen minutes of system operation.<ref name="drdobbs">{{cite web |url=http://www.linuxjournal.com/article/9001 |title=Examining Load Average |first=Ray |last=Walker |date=1 December 2006 |work=Linux Journal |accessdate=13 March 2012 }}</ref>

Mathematically speaking, all three values always average all the system load since the system started up. They all decay exponentially, but they decay at different ''speeds'': they decay exponentially by ''e'' after 1, 5, and 15 minutes respectively. Hence, the 1-minute load average consists of 63% (more precisely: 1 - 1/''e'') of the load from the last minute and 37% (1/''e'') of the average load since start up, excluding the last minute. For the 5- and 15-minute load averages, the same 63%/37% ratio is computed over 5 minutes and 15 minutes respectively. Therefore, it's is not technically accurate that the 1-minute load average only includes the last 60 seconds of activity, (itas actuallyit includes 37% of the activity from the past), but it is correct to state that it includes ''mostly'' the last minute.

For single-CPU systems that are [[CPU bound]], one can think of load average as a measure of system utilization during the respective time period. For systems with multiple CPUs, one must divide the load by the number of processors in order to get a comparable measure.