jm + brendan-gregg   1

Linux Load Averages: Solving the Mystery
Nice bit of OS archaeology by Brendan Gregg.
In 1993, a Linux engineer found a nonintuitive case with load averages, and with a three-line patch changed them forever from "CPU load averages" to what one might call "system load averages." His change included tasks in the uninterruptible state, so that load averages reflected demand for disk resources and not just CPUs. These system load averages count the number of threads working and waiting to work, and are summarized as a triplet of exponentially-damped moving sum averages that use 1, 5, and 15 minutes as constants in an equation. This triplet of numbers lets you see if load is increasing or decreasing, and their greatest value may be for relative comparisons with themselves.
load  monitoring  linux  unix  performance  ops  brendan-gregg  history  cpu 
4 weeks ago by jm

Copy this bookmark: