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Date: Sun, 31 Jul 2011 22:28:29 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: Rick Macklem <rmacklem@uoguelph.ca>
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Cc: FreeBSD-Current <freebsd-current@FreeBSD.org>
Subject: Re: Heavy I/O blocks FreeBSD box for several seconds
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on 31/07/2011 22:03 Rick Macklem said the following:
> Ok, so if the scheduler spin lock is being held too long, what could
> cause this, if it isn't a scheduler bug?
> 
> I can't think of how NFS would affect this beyond causing a heavy I/O
> load, but if there is some way it does, I suppose I need to know what
> that is?

I think I've already referred to the thread on stable@.
This is currently being investigated.

P.S.
Just a pure illustration you can grep for thread_lock to see where else outside
schedulers the sched locks are taken.
-- 
Andriy Gapon