linux-kernel - Re: A unresponsive file system can hang all I/O in the system on linux-2.6.23-rc6 (dirty

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Message-Id: <1190962752.31636.15.camel@twins>
Date:	Fri, 28 Sep 2007 08:59:12 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Chakri n <chakriin5@...il.com>,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>, nfs@...ts.sourceforge.net
Subject: Re: A unresponsive file system can hang all I/O in the system on
	linux-2.6.23-rc6 (dirty_thresh problem?)

On Thu, 2007-09-27 at 23:50 -0700, Andrew Morton wrote:

> 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?

Nasty problem, don't do that :-)

But yeah, with per BDI dirty limits we get stuck at whatever ratio that
NFS server/mount (?) has - which could be 100%. Other processes will
then work almost synchronously against their BDIs but it should work.

[ They will lower the NFS-BDI's ratio, but some fancy clipping code will
  limit the other BDIs their dirty limit to not exceed the total limit.
  And with all these NFS pages stuck, that will still be nothing. ]

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