From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1JfQXf-0004nq-2X for qemu-devel@nongnu.org; Fri, 28 Mar 2008 22:11:35 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1JfQXZ-0004me-Ol for qemu-devel@nongnu.org; Fri, 28 Mar 2008 22:11:33 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1JfQXZ-0004mb-He for qemu-devel@nongnu.org; Fri, 28 Mar 2008 22:11:29 -0400 Received: from mail2.shareable.org ([80.68.89.115]) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1JfQXZ-0006ix-4B for qemu-devel@nongnu.org; Fri, 28 Mar 2008 22:11:29 -0400 Date: Sat, 29 Mar 2008 02:11:26 +0000 From: Jamie Lokier Subject: Re: [kvm-devel] [Qemu-devel] [PATCH] QEMU: fsync AIO writes on flush request 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-Disposition: inline In-Reply-To: <200803290202.54431.paul@codesourcery.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Brook Cc: kvm-devel , qemu-devel@nongnu.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