From: Peter Zijlstra Subject: Re: [PATCH] improve the performance of large sequential write NFS workloads Date: Wed, 06 Jan 2010 20:07:56 +0100 Message-ID: <1262804876.4049.66.camel@laptop> References: <20091222015907.GA6223@localhost> <1261578107.2606.11.camel@localhost> <20091223180551.GD3159@quack.suse.cz> <1261595574.6775.2.camel@localhost> <20091224025228.GA12477@localhost> <1261656281.3596.1.camel@localhost> <20091225055617.GA8595@localhost> <1262190168.7332.6.camel@localhost> <20091231050441.GB19627@localhost> <1262286828.8151.113.camel@localhost> <20100106030346.GA15962@localhost> <1262796962.4251.91.camel@localhost> <1262802387.4251.117.camel@localhost> <1262803040.4049.62.camel@laptop> <1262803927.4251.133.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Wu Fengguang , Jan Kara , Steve Rago , "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "jens.axboe" , Peter Staubach , Arjan van de Ven , Ingo Molnar , "linux-fsdevel@vger.kernel.org" To: Trond Myklebust Return-path: In-Reply-To: <1262803927.4251.133.camel@localhost> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, 2010-01-06 at 13:52 -0500, Trond Myklebust wrote: > 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? The bdi_stat_sum() in the error limit is basically the only such expensive op, but I suspect we might hit that more than enough. So sure that sounds like a plan.