Intermittent system hangs on 7.2-RELEASE-p1

John Baldwin jhb at freebsd.org
Wed Aug 26 20:43:54 UTC 2009


On Wednesday 26 August 2009 3:03:13 pm Linda Messerschmidt wrote:
> I'm trying to troubleshoot an intermittent Apache performance problem,
> and I've narrowed it down using to what appears to be a brief
> whole-system hang that last from 0.5 - 3 seconds.  They occur every
> few minutes.

One thing to note is that ktrace only logs voluntary context switches (i.e. 
call to tsleep or waiting on a condition variable).  It specifically does not 
log preemptions or blocking on a mutex, so in theory if your machine was 
livelocked temporarily that might explain this.

-- 
John Baldwin


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