linux-kernel - Re: high latency NFS

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Message-ID: <4896CB22.4000005@melbourne.sgi.com>
Date:	Mon, 04 Aug 2008 19:25:54 +1000
From:	Greg Banks <gnb@...bourne.sgi.com>
To:	Bernd Schubert <bs@...eap.de>
CC:	"J. Bruce Fields" <bfields@...ldses.org>,
	Neil Brown <neilb@...e.de>, Michael Shuey <shuey@...due.edu>,
	Shehjar Tikoo <shehjart@....unsw.edu.au>,
	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
	rees@...i.umich.edu, aglo@...i.umich.edu
Subject: Re: high latency NFS

Bernd Schubert wrote:
> On Monday 04 August 2008 03:11:58 J. Bruce Fields wrote:
>   
>> OK, so to summarize: when the rate of incoming rpc's is very high (and,
>> I guess, when we're serving everything out of cache and don't have IO
>> wait), all the nfsd threads will stay runable all the time.  That keeps
>> userspace processes from running (possibly for "minutes").  And that's a
>> problem even on a server dedicated only to nfs, since it affects portmap
>> and rpc.mountd.
>>     
>
> Even worse, it affects user space HA software such as heartbeat and everyone 
> with reasonable timeouts will see spurious 'failures'. 
>   
We're seeing that problem right now, even with the patch.

-- 
Greg Banks, P.Engineer, SGI Australian Software Group.
The cake is *not* a lie.
I don't speak for SGI.

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