high load system do not take all CPU time

[Daniel Staal]

--As of December 17, 2011 10:29:42 AM +0200, Коньков Евгений 
is alleged to have said:

> How to debug why system do not use free CPU resouces?
>
> On this pictures you can see that CPU can not exceed 400tics
> http://piccy.info/view3/2368839/c9022754d5fcd64aff04482dd360b5b2/
> http://piccy.info/view3/2368837/a12aeed98681ed10f1a22f5b5edc5abc/
> http://piccy.info/view3/2368836/da6a67703af80eb0ab8088ab8421385c/
>
>
> On these pictures you can see that problems begin with trafic on re0
> when CPU load rise to "maximum"
> http://piccy.info/view3/2368834/512139edc56eea736881affcda490eca/
> http://piccy.info/view3/2368827/d27aead22eff69fd1ec2b6aa15e2cea3/
>
> But there is 25% CPU idle yet at that moment.

<snip>

># top -SIHP
> last pid: 93050;  load averages:  1.45,  1.41,  1.29
> up 9+16:32:06  10:28:43 237 processes: 5 running, 210 sleeping, 2
> stopped, 20 waiting
> CPU 0:  0.8% user,  0.0% nice,  8.7% system, 17.7% interrupt, 72.8% idle
> CPU 1:  0.0% user,  0.0% nice,  9.1% system, 20.1% interrupt, 70.9% idle
> CPU 2:  0.4% user,  0.0% nice,  9.4% system, 19.7% interrupt, 70.5% idle
> CPU 3:  1.2% user,  0.0% nice,  6.3% system, 22.4% interrupt, 70.1% idle
> Mem: 843M Active, 2476M Inact, 347M Wired, 150M Cache, 112M Buf, 80M Free
> Swap: 4096M Total, 15M Used, 4080M Free

--As for the rest, it is mine.

You are I/O bound; most of your time is spent in interrupts.  The CPU is 
dealing with things as fast as it can get them, but it has to wait for the 
disk and/or network card to get them to it.  The CPU is not your problem; 
if you need more performance, you need to tune the I/O.  (And possibly get 
better I/O cards, if available.)

Daniel T. Staal

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