Messages in this thread | | | Date | Sun, 13 Oct 2002 14:31:05 +0200 | From | Marius Gedminas <> | Subject | Re: Strange load spikes on 2.4.19 kernel |
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On Sun, Oct 13, 2002 at 04:34:21PM +1000, Rob Mueller wrote: > Also Let me do a calculation, though I have no idea if this is right or > not... > a) the first item in the uptime output is 'system load average for the last > 1 minute' > b) it seems to only update/recalculate every 5 seconds > c) it jumps from < 1 to 20 in 1 interval (eg 5 seconds) > > This means that for it to jump from < 1 to 20 in 5 seconds, there must be on > average about 60/5 * 20 = 240 processes blocked over those 5 seconds waiting > for run time of some sort for the load to jump 20 points. Is that right?
Load is an exponential average, recalculated according to this formula (see CALC_LOAD in sched.h) every five seconds:
load1 = load1 * exp + n * (1 - exp)
where exp = 1/exp(5sec/1min) ~= 1884/2048 ~= 0.92 n = the number of running tasks at the moment
To jump from 0.21 to 27.65 in 5 second (1 update), n would have to be 343. Wow. (Substituting the numbers for 5 and 15 minute averages I get n of about 362 and 352).
Can somebody check my math?
Marius Gedminas -- Never trust a computer you can't repair yourself.
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