Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262570AbVDAC2j (ORCPT ); Thu, 31 Mar 2005 21:28:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262572AbVDAC2j (ORCPT ); Thu, 31 Mar 2005 21:28:39 -0500 Received: from viper.oldcity.dca.net ([216.158.38.4]:59055 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S262570AbVDAC2h (ORCPT ); Thu, 31 Mar 2005 21:28:37 -0500 Subject: Re: NFS client latencies From: Lee Revell To: Ingo Molnar Cc: Trond Myklebust , Andrew Morton , linux-kernel@vger.kernel.org In-Reply-To: <20050331145015.GA4830@elte.hu> References: <1112237239.26732.8.camel@mindpipe> <1112240918.10975.4.camel@lade.trondhjem.org> <20050331065942.GA14952@elte.hu> <20050330231801.129b0715.akpm@osdl.org> <20050331073017.GA16577@elte.hu> <1112270304.10975.41.camel@lade.trondhjem.org> <1112272451.10975.72.camel@lade.trondhjem.org> <20050331135825.GA2214@elte.hu> <1112279522.20211.8.camel@lade.trondhjem.org> <20050331143930.GA4032@elte.hu> <20050331145015.GA4830@elte.hu> Content-Type: text/plain Date: Thu, 31 Mar 2005 21:28:36 -0500 Message-Id: <1112322516.2509.28.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.2.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1114 Lines: 28 On Thu, 2005-03-31 at 16:50 +0200, Ingo Molnar wrote: > * Ingo Molnar wrote: > > > > So the overhead you are currently seeing should just be that of > > > iterating through the list, locking said requests and adding them to > > > our private list. > > > > ah - cool! This was a 100 MB writeout so having 3.7 msecs to process > > 20K+ pages is not unreasonable. To break the latency, can i just do a > > simple lock-break, via the patch below? > > with this patch the worst-case latency during NFS writeout is down to 40 > usecs (!). > > Lee: i've uploaded the -42-05 release with this patch included - could > you test it on your (no doubt more complex than mine) NFS setup? This fixes all the NFS related latency problems I was seeing. Now the longest latency from an NFS kernel compile with "make -j64" is 391 usecs in get_swap_page. Lee - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/