Revision as of 17:32, 23 May 2025 edit Comp.arch (talk \| contribs) Extended confirmed users 41,514 edits mNo edit summary Tag: 2017 wikitext editor ← Previous edit		Latest revision as of 17:40, 23 May 2025 edit undo Comp.arch (talk \| contribs) Extended confirmed users 41,514 edits m →Reckoning CPU load: Hz is correct upper case, while lower as hertz. Tag: 2017 wikitext editor
Line 55: == Reckoning CPU load == On Linux systems, the load-average is not calculated on each clock tick, but driven by a variable value that is based on the HZ frequency setting and tested on each clock tick. This setting defines the kernel clock tick rate in [[~~Hertz~~hertz]] (times per second), and it defaults to 100 for ~~10ms~~10 ms ticks. Kernel activities use this number of ticks to time themselves. Specifically, the timer.c::calc_load() function, which calculates the load average, runs every {{tt\|1=LOAD_FREQ = (5HZ+1)}} ticks, or about every five seconds: <syntaxhighlight lang="c"> Line 94: The "sampled" calculation of load averages is a somewhat common behavior; FreeBSD, too, only refreshes the value every five seconds. The interval is usually taken to not be exact so that they do not collect processes that are scheduled to fire at a certain moment.<ref>{{cite web \|title=How is load average calculated on FreeBSD? \|url=https://unix.stackexchange.com/a/342778 \|website=Unix & Linux Stack Exchange}}</ref> A post on the Linux mailing list considers its {{tt\|+1}} tick insufficient to avoid ~~Moire~~[[Moiré pattern\|Moiré artifacts]] from such collection, and suggests an interval of 4.61 seconds instead.<ref>{{cite web \|last1=Ripke \|first1=Klaus \|title=Linux-Kernel Archive: LOAD_FREQ (4HZ+61) avoids loadavg Moire \|url=https://lkml.iu.edu/hypermail/linux/kernel/1111.1/02446.html \|website=lkml.iu.edu \|date=2011}} [https://ripke.com/loadavg/moire graph & patch<!-- Actual title at target: Moiré patterns in linux load average (Moiré mangled in title as MoirÃ©) -->]</ref> This change is common among [[Android (operating system)\|Android system]] kernels, although the exact expression used assumes an HZ of 100.<ref>{{cite web \|title=Patch kernel with the 4.61s load thing · Issue #2109 · AOSC-Dev/aosc-os-abbs \|url=https://github.com/AOSC-Dev/aosc-os-abbs/issues/2109 \|website=GitHub \|language=en}}</ref> == Other system performance commands ==

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