From: Peter Zijlstra <a.p.zijlstra@chello.nl>
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 20:48:59 +0200
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	 <20070927235034.ae7bd73d.akpm@linux-foundation.org>
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Cc: Trond Myklebust <trond.myklebust@fys.uio.no>,
	Chakri n <chakriin5@gmail.com>,
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To: Andrew Morton <akpm@linux-foundation.org>
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On Fri, 2007-09-28 at 11:49 -0700, Andrew Morton wrote:

> Do you know where the stalls are occurring?  throttle_vm_writeout(), or via
> direct calls to congestion_wait() from page_alloc.c and vmscan.c?  (running
> sysrq-w five or ten times will probably be enough to determine this)

would it make sense to instrument congestion_wait() callsites with
vmstats?