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Date: Tue, 18 Dec 2007 08:57:32 -0800
From: David G Lawrence <dg@dglawrence.com>
To: Bruce Evans <brde@optusnet.com.au>
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Cc: freebsd-net@FreeBSD.org, freebsd-stable@FreeBSD.org
Subject: Re: Packet loss every 30.999 seconds
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> I got an almost identical delay (with 64000 vnodes).
> 
> Now, 17ms isn't much.

   Says you. On modern systems, trying to run a pseudo real-time application
on an otherwise quiescent system, 17ms is just short of an eternity. I agree
that the syncer should be preemptable (which is what my bandaid patch
attempts to do), but that probably wouldn't have helped my specific problem
since my application was a user process, not a kernel thread.
   All of my systems have options PREEMPTION - that is the default in
6+. It doesn't affect this problem.
   On the other hand, the syncer shouldn't be consuming this much CPU in
the first place. There is obviously a bug here. Of course looking through
all of the vnodes in the system for something dirty is stupid in the
first place; there should be a seperate list for that. ...but a simple
fix is what is needed right now.
   I'm going to have to bow out of this discussion now. I just don't have
the time for it.

-DG

David G. Lawrence
President
Download Technologies, Inc. - http://www.downloadtech.com - (866) 399 8500
The FreeBSD Project - http://www.freebsd.org
Pave the road of life with opportunities.