From xen-devel-bounces@lists.xen.org Wed Feb 19 11:22:54 2014 Received: (at maildrop) by bugs.xenproject.org; 19 Feb 2014 11:22:54 +0000 Received: from lists.xen.org ([50.57.142.19]) by bugs.xenproject.org with esmtp (Exim 4.80) (envelope-from ) id 1WG5Es-0003yw-44 for xen-devel-maildrop-Eithu9ie@bugs.xenproject.org; Wed, 19 Feb 2014 11:22:54 +0000 Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WG5A1-0003or-7z; Wed, 19 Feb 2014 11:17:53 +0000 Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WG59z-0003oi-Qy for xen-devel@lists.xen.org; Wed, 19 Feb 2014 11:17:52 +0000 Received: from [85.158.137.68:44236] by server-4.bemta-3.messagelabs.com id 5E/24-04858-ED294035; Wed, 19 Feb 2014 11:17:50 +0000 X-Env-Sender: George.Dunlap@citrix.com X-Msg-Ref: server-13.tower-31.messagelabs.com!1392808668!1588967!1 X-Originating-IP: [66.165.176.63] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogNjYuMTY1LjE3Ni42MyA9PiAzMDYwNDg=\n X-StarScan-Received: X-StarScan-Version: 6.9.16; banners=-,-,- X-VirusChecked: Checked Received: (qmail 6252 invoked from network); 19 Feb 2014 11:17:50 -0000 Received: from smtp02.citrix.com (HELO SMTP02.CITRIX.COM) (66.165.176.63) by server-13.tower-31.messagelabs.com with RC4-SHA encrypted SMTP; 19 Feb 2014 11:17:50 -0000 X-IronPort-AV: E=Sophos;i="4.97,505,1389744000"; d="scan'208";a="102139276" Received: from accessns.citrite.net (HELO FTLPEX01CL02.citrite.net) ([10.9.154.239]) by FTLPIPO02.CITRIX.COM with ESMTP; 19 Feb 2014 11:17:48 +0000 Received: from ukmail1.uk.xensource.com (10.80.16.128) by smtprelay.citrix.com (10.13.107.79) with Microsoft SMTP Server id 14.2.342.4; Wed, 19 Feb 2014 06:17:48 -0500 Received: from elijah.uk.xensource.com ([10.80.2.24]) by ukmail1.uk.xensource.com with esmtp (Exim 4.69) (envelope-from ) id 1WG59u-0004Mu-Tc; Wed, 19 Feb 2014 11:17:46 +0000 Message-ID: <530492D7.6050503@eu.citrix.com> Date: Wed, 19 Feb 2014 11:17:43 +0000 From: George Dunlap User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Jan Beulich , Yang Z Zhang References: <20140210080314.GA758@deinos.phlegethon.org> <20140211090202.GC92054@deinos.phlegethon.org> <20140211115553.GB97288@deinos.phlegethon.org> <52FA2C63020000780011B201@nat28.tlf.novell.com> <52FA480D.9040707@eu.citrix.com> <52FCE8BE.8050105@eu.citrix.com> <52FCF90F020000780011C29A@nat28.tlf.novell.com> <20140213162022.GE82703@deinos.phlegethon.org> <5301F000020000780011CCE0@nat28.tlf.novell.com> <53022209.1060005@eu.citrix.com> <5302332D020000780011CEF1@nat28.tlf.novell.com> <53033544.2000409@eu.citrix.com> <53047F74020000780011D8E4@nat28.tlf.novell.com> <53048F96.7010503@eu.citrix.com> <53049FD3020000780011DA37@nat28.tlf.novell.com> In-Reply-To: <53049FD3020000780011DA37@nat28.tlf.novell.com> X-DLP: MIA2 Cc: "andrew.cooper3@citrix.com" , Tim Deegan , Xiantao Zhang , Donald D Dugger , "xen-devel@lists.xen.org" Subject: Re: [Xen-devel] [PATCH] Don't track all memory when enabling log dirty to track vram X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org On 02/19/2014 11:13 AM, Jan Beulich wrote: >>>> On 19.02.14 at 12:03, George Dunlap wrote: >> On 02/19/2014 08:55 AM, Jan Beulich wrote: >>>>>> On 19.02.14 at 02:28, "Zhang, Yang Z" wrote: >>>> George Dunlap wrote on 2014-02-18: >>>>> On 02/18/2014 03:14 AM, Zhang, Yang Z wrote: >>>>> perhaps my original patch is better which will check >>>>> paging_mode_log_dirty(d) && log_global: >>>>> >>>>> It turns out that the reason I couldn't get a crash was because libxc >>>>> was actually paying attention to the -EINVAL return value, and >>>>> disabling and then re-enabling logdirty. That's what would happen >>>>> before your dirty vram patch, and that's what happens after. And >>>>> arguably, that's the correct behavior for any toolstack, given that the >>>> interface returns an error. >>>> >>>> Agree. >>>> >>>>> This patch would actually change the interface; if we check this in, >>>>> then if you enable logdirty when dirty vram tracking is enabled, you >>>>> *won't* get an error, and thus *won't* disable and re-enable logdirty mode. >>>>> So actually, this patch would be more disruptive. >>>>> >>>> Jan, do you have any comment? >>> This simplistic variant is just calling for problems. As was already >>> said elsewhere on this thread, we should simply do the mode change >>> properly: Track that a partial log-dirty mode is in use, and allow >>> switching to global log-dirty mode (converting all entries to R/O). >> I think Yang was asking you for your opinion on my suggestion that >> nothing actually needed to be done. Enabling full logdirty mode for >> migration when dirty vram tracking was enabled has *always* returned an >> error (or at least for a long time now), and *always* resulted in the >> toolstack disabling and re-enabling logdirty mode; Yang's patch doesn't >> change that at all. >> >> If you think that's an interface we need to improve in the future, we >> can put it on the list of improvements. But at this point it seems to >> me more like a nice-to-have. > I agree - for 4.4.0 we shouldn't need any further adjustments. And > I hoped to imply that I don't see a need for this incremental change > to go in by having said "This simplistic variant is just calling for > problems". No, but "we should simply do the mode change properly" could be interpreted as saying, "this needs to be done as a follow-up to the dirty vram tracking patch"; someone might even interpret it as, "you need to do this as a follow-up". That's what I was trying to clarify / express an opinion on. :-) -George _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel