From mboxrd@z Thu Jan  1 00:00:00 1970
From: Trond Myklebust <Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH] improve the performance of large sequential write NFS
 workloads
Date: Wed, 06 Jan 2010 13:52:07 -0500
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Cc: Wu Fengguang <fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
	Steve Rago <sar-a+KepyhlMvJWk0Htik3J/w@public.gmane.org>,
	"linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"jens.axboe" <jens.axboe-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	Peter Staubach <staubach-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Arjan van de Ven <arjan-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>,
	"linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
To: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
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List-Id: linux-fsdevel.vger.kernel.org

On Wed, 2010-01-06 at 19:37 +0100, Peter Zijlstra wrote: 
> On Wed, 2010-01-06 at 13:26 -0500, Trond Myklebust wrote:
> > OK. It looks as if the only key to finding out how many unstable writes
> > we have is to use global_page_state(NR_UNSTABLE_NFS), so we can't
> > specifically target our own backing-dev. 
> 
> Would be a simple matter of splitting BDI_UNSTABLE out from
> BDI_RECLAIMABLE, no?
> 
> Something like

OK. How about if we also add in a bdi->capabilities flag to tell that we
might have BDI_UNSTABLE? That would allow us to avoid the potentially
expensive extra calls to bdi_stat() and bdi_stat_sum() for the non-nfs
case?

Cheers
   Trond
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