Return-Path: Received: from mail-out1.uio.no ([129.240.10.57]:52563 "EHLO mail-out1.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751151AbZFDU50 (ORCPT ); Thu, 4 Jun 2009 16:57:26 -0400 Subject: Re: Link performance over NFS degraded in RHEL5. -- was : Read/Write NFS I/O performance degraded by FLUSH_STABLE page flushing From: Trond Myklebust To: Brian R Cowan Cc: Carlos Carvalho , linux-nfs@vger.kernel.org, linux-nfs-owner@vger.kernel.org In-Reply-To: References: <1243615595.7155.48.camel@heimdal.trondhjem.org> <1243618500.7155.56.camel@heimdal.trondhjem.org> <1243686363.5209.16.camel@heimdal.trondhjem.org> <1243963631.4868.124.camel@heimdal.trondhjem.org> <18982.41770.293636.786518@fisica.ufpr.br> <1244049027.5603.5.camel@heimdal.trondhjem.org> Content-Type: text/plain Date: Thu, 04 Jun 2009 16:57:22 -0400 Message-Id: <1244149042.5203.108.camel@heimdal.trondhjem.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Thu, 2009-06-04 at 16:43 -0400, Brian R Cowan wrote: > What I'm trying to understand is why RHEL 4 is not flushing anywhere near > as often. Either RHEL4 erred on the side of not writing, and RHEL5 is > erring on the opposite side, or RHEL5 is doing unnecessary flushes... I've > seen that 2.6.29 flushes less than the Red hat 2.6.18-derived kernels, but > it still flushes a lot more than RHEL 4 does. Most of that increase is probably mainly due to the changes to the way stat() works. More precisely, it would be due to this patch: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git&a=commitdiff&h=70b9ecbdb9c5fdc731f8780bffd45d9519020c4a which went into Linux 2.6.16 in order to fix a posix compatibility issue. Trond