cpu usage in 7.0

Daniel Gerzo danger at FreeBSD.org
Mon Feb 25 08:45:33 UTC 2008

Hello Jeff,

Sunday, February 24, 2008, 11:47:39 PM, you wrote:

>> So how does a multithreaded process get 458% CPU on a quad-core machine? :) 
>> (Really, I want to know; I thought thread CPU accounting was fixed in 7.x. 
>> Unless I'm mistaken, 4 CPU-intensive threads in a single process should 
>> account as 4 CPU-intensive single-thread processes; i.e. each could only take 
>> up to 100% of a core/CPU, accounting for NCPU*100% total).

> It is possible for the sum of all threads in the system to exceed 100%
> cpu.  This is because the decay function is not precise.  15% over is a
> bit more than I would expect but I suppose it's possible.  We also inhert
> pcpu information from the parent on fork/thread creation so the child 
> isn't created with a priority as if it had been idle.  So for a moment the
> utilization is duplicated.

I have a box running mysqld, which sometimes exeeds 130%, what about
this? ;)

Also the mysqld is alsmost all the time in the "ucond" state, what
does it mean? I've been told that it is probably waiting for I/O, but
then, I have another box which is currently completely idle, but
running mysql shows that it is "ucond" as well.

Best regards,
 Daniel                            mailto:danger at FreeBSD.org

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