Load (computing): Difference between revisions

Revision as of 00:36, 10 January 2019

Revision as of 22:23, 1 February 2019

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14:34:03 up 10:43, 4 users, load average: 0.06, 0.11, 0.09

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The [[W (Unix)|<tt>w</tt>]] and [[Top (Unix)|<tt>top</tt>]] commands show the same three load average numbers, as do a range of [[graphical user interface]] utilities. In [[GNU/Linux]], they can also be accessed by reading the [[procfs|<code>/proc/loadavg</code>]] file.

An idle computer has a load number of 0 (the idle process isn't counted). Each [[process (computing)|process]] using or waiting for [[Central processing unit|CPU]] (the ''ready queue'' or [[run queue]]) increments the load number by 1. Each process that terminates decrements it by 1. Most UNIX systems count only processes in the ''running'' (on CPU) or ''runnable'' (waiting for CPU) [[Process states|states]]. However, Linux also includes processes in [[uninterruptible sleep]] states (usually waiting for [[Hard disk|disk]] activity), which can lead to markedly different results if many processes remain blocked in [[Input/output|I/O]] due to a busy or stalled I/O system.<ref>http://linuxtechsupport.blogspot.com/2008/10/what-exactly-is-load-average.html</ref> This, for example, includes processes blocking due to an [[Network File System (protocol)|NFS]] server failure or too slow [[Data storage device|media]] (e.g., [[Universal Serial Bus|USB]] 1.x storage devices). Such circumstances can result in an elevated load average which does not reflect an actual increase in CPU use (but still gives an idea of how long users have to wait).