From: Chuck Lever Subject: Re: Read/Write NFS I/O performance degraded by FLUSH_STABLE page flushing Date: Tue, 2 Jun 2009 11:00:25 -0400 Message-ID: References: <5ECD2205-4DC9-41F1-AC5C-ADFA984745D3@oracle.com> <49FA0CE8.9090706@redhat.com> <1241126587.15476.62.camel@heimdal.trondhjem.org> <1243615595.7155.48.camel@heimdal.trondhjem.org> <1243618500.7155.56.camel@heimdal.trondhjem.org> <1243686363.5209.16.camel@heimdal.trondhjem.org> Mime-Version: 1.0 (Apple Message framework v935.3) Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Cc: Trond Myklebust , Brian R Cowan , linux-nfs@vger.kernel.org, linux-nfs-owner@vger.kernel.org, Peter Staubach To: Greg Banks Return-path: Received: from rcsinet11.oracle.com ([148.87.113.123]:34735 "EHLO rgminet11.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753934AbZFBPAu (ORCPT ); Tue, 2 Jun 2009 11:00:50 -0400 In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On May 30, 2009, at 9:02 AM, Greg Banks wrote: > On Sat, May 30, 2009 at 10:26 PM, Trond Myklebust > wrote: >> On Sat, 2009-05-30 at 10:22 +1000, Greg Banks wrote: >>> On Sat, May 30, 2009 at 3:35 AM, Trond Myklebust >>> wrote: >>>> On Fri, 2009-05-29 at 13:25 -0400, Brian R Cowan wrote: >>>>> >>> >> >> Firstly, the server only uses O_SYNC if you turn off write gathering >> (a.k.a. the 'wdelay' option). The default behaviour for the Linux nfs >> server is to always try write gathering and hence no O_SYNC. > > Well, write gathering is a total crock that AFAICS only helps > single-file writes on NFSv2. For today's workloads all it does is > provide a hotspot on the two global variables that track writes in an > attempt to gather them. Back when I worked on a server product, > no_wdelay was one of the standard options for new exports. Really? Even for NFSv3/4 FILE_SYNC? I can understand that it wouldn't have any real effect on UNSTABLE. -- Chuck Lever chuck[dot]lever[at]oracle[dot]com