From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= Subject: Re: [PATCH] libxl: prefer qdisk over blktap when choosing disk backend Date: Wed, 28 Aug 2013 17:04:07 +0200 Message-ID: <521E1167.40404@citrix.com> References: <1377613363-5582-1-git-send-email-wei.liu2@citrix.com> <20130828091538.GD15729@zion.uk.xensource.com> <21021.53894.805398.918930@mariner.uk.xensource.com> <521DE4BB.9010404@m2r.biz> <21021.62804.505685.545182@mariner.uk.xensource.com> <521DF827.4000800@m2r.biz> <20130828133556.GH15729@zion.uk.xensource.com> <20130828134113.GI15729@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1VEhI3-00064k-Ih for xen-devel@lists.xenproject.org; Wed, 28 Aug 2013 15:04:11 +0000 In-Reply-To: <20130828134113.GI15729@zion.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Wei Liu Cc: George Dunlap , xen-devel , Fabio Fantoni , Ian Jackson , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On 28/08/13 15:41, Wei Liu wrote: > On Wed, Aug 28, 2013 at 02:35:56PM +0100, Wei Liu wrote: >> On Wed, Aug 28, 2013 at 03:16:23PM +0200, Fabio Fantoni wrote: >>> Il 28/08/2013 15:04, Ian Jackson ha scritto: >>>> Fabio Fantoni writes ("Re: [Xen-devel] [PATCH] libxl: prefer qdisk over blktap when choosing disk backend"): >>>>> I think is good prefer qdisk also for significant performance increase >>>>> in comparison with blktap2. >>>> Thanks, that's useful information. That, and what George said, have >>>> convinced me this is the right change. >>>> >>>> Acked-by: Ian Jackson >>> >>> What about qemu traditional with this patch? >>> I haven't tested qdisk with qemu traditional but unfortunately >>> qemu-trad. is still widely used and therefore you have to be sure >>> that does not cause problems. >> >> Ah, now I get your question. >> >>> I asked about because devices parts seem the same with both qemu but >>> I not sure about it. >> >> We've already switched to qemu-upstream in 4.3. And this patch is not >> backport material so old system would just work fine IMHO. >> >> The only risk of breakage is: users have device_model_version set to >> qemu-trad and run blktap kernel with Xen pre-4.3, then upgrade to Xen >> post-4.3 (with this patch). I've tested that, and qemu-trad runs fine >> for me -- at least it boots and dd works well. >> > > I didn't have a VHD image (format commonly supported by blktap and qemu) > at hand so the test was not complete. But qemu-trad and qemu-xen are > both maintained so even if it breaks we are able to fix them -- which is > main point of this patch, to let users have better supported backend. I might be completely wrong, but wasn't there a problem when using blktap VHD images with Qemu (ie VHD images created with blktap weren't copatible with VHD Qemu implementation)?