From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.netapp.com ([216.240.18.37]:5681 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755764Ab1CRCZJ convert rfc822-to-8bit (ORCPT ); Thu, 17 Mar 2011 22:25:09 -0400 Subject: Re: Small O_SYNC writes are no longer NFS_DATA_SYNC From: Trond Myklebust To: NeilBrown Cc: linux-nfs@vger.kernel.org In-Reply-To: <20110318131214.0e2c840a@notabene.brown> References: <20110216171555.6642c630@notabene.brown> <1300405987.4621.10.camel@lade.trondhjem.org> <20110318120417.435551da@notabene.brown> <1300412966.9671.9.camel@lade.trondhjem.org> <20110318131214.0e2c840a@notabene.brown> Content-Type: text/plain; charset="UTF-8" Date: Thu, 17 Mar 2011 22:25:08 -0400 Message-ID: <1300415108.13476.6.camel@lade.trondhjem.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Fri, 2011-03-18 at 13:12 +1100, NeilBrown wrote: > On Thu, 17 Mar 2011 21:49:26 -0400 Trond Myklebust > wrote: > > > However we could adopt the Solaris convention of always starting > > writebacks with a FILE_SYNC, and then falling back to UNSTABLE for the > > second rpc call and all subsequent calls... > > > > That approach certainly has merit. > > However, as we know from the wbc info whether the write is small and sync - > which is the only case where I think a STABLE write is needed - I cannot see > why you don't want to just use that information to guide the choice of > 'stable' or not ??? By far the most common case we would want to optimise for is the sync at close() or fsync() when you have written a small file (<= wsize). If we can't optimise for that case, then the optimisation isn't worth doing at all. The point is that in that particular case, the wbc doesn't help you at all since the limits are set at 0 and LLONG_MAX (see nfs_wb_all(), write_inode_now(),...) -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@netapp.com www.netapp.com