Subject: Re: [PATCH] sched: Fix adverse effects of NFS client on
	interactive response
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Peter Williams <pwil3058@bigpond.net.au>
Cc: Ingo Molnar <mingo@elte.hu>, Con Kolivas <kernel@kolivas.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <43A8EF87.1080108@bigpond.net.au>
References: <43A8EF87.1080108@bigpond.net.au>
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Date: Wed, 21 Dec 2005 01:09:01 -0500
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On Wed, 2005-12-21 at 17:00 +1100, Peter Williams wrote:
> This patch addresses the adverse effect that the NFS client can have on 
> interactive response when CPU bound tasks (such as a kernel build) 
> operate on files mounted via NFS.  (NB It is emphasized that this has 
> nothing to do with the effects of interactive tasks accessing NFS 
> mounted files themselves.)
> 
> The problem occurs because tasks accessing NFS mounted files for data 
> can undergo quite a lot of TASK_INTERRUPTIBLE sleep depending on the 
> load on the server and the quality of the network connection.  This can 
> result in these tasks getting quite high values for sleep_avg and 
> consequently a large priority bonus.  On the system where I noticed this 
> problem they were getting the full 10 bonus points and being given the 
> same dynamic priority as genuine interactive tasks such as the X server 
> and rythmbox.
> 
> The solution to this problem is to use TASK_NONINTERACTIVE to tell the 
> scheduler that the TASK_INTERRUPTIBLE sleeps in the NFS client and 
> SUNRPC are NOT interactive sleeps.

Sorry. That theory is just plain wrong. ALL of those case _ARE_
interactive sleeps.

Cheers,
  Trond

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