From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: A unresponsive file system can hang all I/O in the system on
	linux-2.6.23-rc6 (dirty_thresh problem?)
Date: Fri, 28 Sep 2007 13:00:53 -0400
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	 <20070927235034.ae7bd73d.akpm@linux-foundation.org>
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Cc: Chakri n <chakriin5@gmail.com>,
	linux-pm <linux-pm@lists.linux-foundation.org>,
	lkml <linux-kernel@vger.kernel.org>, nfs@lists.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Andrew Morton <akpm@linux-foundation.org>
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On Thu, 2007-09-27 at 23:50 -0700, Andrew Morton wrote:

> Actually we perhaps could address this at the VFS level in another way. 
> Processes which are writing to the dead NFS server will eventually block in
> balance_dirty_pages() once they've exceeded the memory limits and will
> remain blocked until the server wakes up - that's the behaviour we want.
> 
> What we _don't_ want to happen is for other processes which are writing to
> other, non-dead devices to get collaterally blocked.  We have patches which
> might fix that queued for 2.6.24.  Peter?

Do these patches also cause the memory reclaimers to steer clear of
devices that are congested (and stop waiting on a congested device if
they see that it remains congested for a long period of time)? Most of
the collateral blocking I see tends to happen in memory allocation...

Cheers
  Trond