From: Ingo Molnar Subject: Re: [PATCH] improve the performance of large sequential write NFS workloads Date: Fri, 18 Dec 2009 20:41:29 +0100 Message-ID: <20091218194129.GB6153@elte.hu> References: <1261015420.1947.54.camel@serenity> <1261037877.27920.36.camel@laptop> <1261164799.1947.123.camel@serenity> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Trond.Myklebust@netapp.com, Wu Fengguang , "jens.axboe" To: Steve Rago Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:51503 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750946AbZLRTlr (ORCPT ); Fri, 18 Dec 2009 14:41:47 -0500 In-Reply-To: <1261164799.1947.123.camel@serenity> Sender: linux-nfs-owner@vger.kernel.org List-ID: * Steve Rago wrote: > > Also, I don't think this needs to have a sysctl, it should just work. > > The sysctl is a *good thing* in that it allows the eager writeback behavior > to be tuned and shut off if need be. I can only test the changes on a > finite set of systems, so better safe than sorry. This issue has been settled many years ago and that's not what we do in the Linux kernel. We prefer patches to core code where we are reasonably sure they result in good behavior - and then we fix bugs in the new behavior, if any. (Otherwise odd sysctls would mushroom quickly and the system would become untestable in practice.) Ingo