From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [RFC] relaxed barrier semantics Date: Thu, 29 Jul 2010 22:03:27 +0200 Message-ID: <20100729200327.GA17767@lst.de> References: <20100728085048.GA8884@lst.de> <4C4FF136.5000205@kernel.org> <20100728090025.GA9252@lst.de> <4C4FF592.9090800@kernel.org> <20100728092859.GA11096@lst.de> <20100729014431.GD4506@thunk.org> <4C51DA1F.2040701@redhat.com> <20100729194904.GA17098@lst.de> <4C51DCF1.3010507@redhat.com> <1280433591.4441.393.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ric Wheeler , Christoph Hellwig , "Ted Ts'o" , Tejun Heo , Vivek Goyal , Jan Kara , jaxboe@fusionio.com, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp To: James Bottomley Return-path: Received: from verein.lst.de ([213.95.11.210]:43542 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752579Ab0G2UDz (ORCPT ); Thu, 29 Jul 2010 16:03:55 -0400 Content-Disposition: inline In-Reply-To: <1280433591.4441.393.camel@mulgrave.site> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, Jul 29, 2010 at 02:59:51PM -0500, James Bottomley wrote: > That's basically everything FUA ... you might just as well switch your > cache to write through and have done. > > This, by the way, is one area I'm hoping to have researched on SCSI > (where most devices do obey the caching directives). Actually see if > write through without flush barriers is faster than writeback with flush > barriers. I really suspect it is. We have done the research and at least for XFS a write through cache actually is faster for many workloads. Ric always has workloads where the cache is faster, though - mostly doing lots of small file write kind of setups.