From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [Qemu-devel] [PATCH] QEMU: fsync AIO writes on flush request Date: Sat, 29 Mar 2008 02:11:26 +0000 Message-ID: <20080329021126.GD30219@shareable.org> References: <20080328150517.GA18077@dmt> <20080328181311.GA19547@dmt> <20080329011751.GB30219@shareable.org> <200803290202.54431.paul@codesourcery.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel , qemu-devel@nongnu.org To: Paul Brook Return-path: Content-Disposition: inline In-Reply-To: <200803290202.54431.paul@codesourcery.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Paul Brook wrote: > > That'll depend on what kind of device is emulated. Does the SCSI > > emulation handle multiple in-flight commands with any guarantee on > > order? > > SCSI definitely allows (and we emulate) multiple in flight commands. > I can't find any requirement that writes must complete before a > subsequent SYNCHRONISE_CACHE. However I don't claim to know the spec > that well, Aren't there SCSI tagged barrier commands or something like that, which allow a host to request ordering between commands? > it's probably not a bad idea have them complete anyway. Preferably > this would be a completely asynchronous operation. i.e. the sync > command returns immediately, but only completes when all preceding > writes have completed and been flushed to disk. I agree, that seems the optimal implementation. -- Jamie ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace