Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752153Ab3DJEck (ORCPT ); Wed, 10 Apr 2013 00:32:40 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:58672 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751974Ab3DJEci (ORCPT ); Wed, 10 Apr 2013 00:32:38 -0400 Message-ID: <5164EB5F.80403@linux.vnet.ibm.com> Date: Wed, 10 Apr 2013 00:32:31 -0400 From: "Michael R. Hines" User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: Roland Dreier , Jason Gunthorpe , Sean Hefty , Hal Rosenstock , Yishai Hadas , Christoph Lameter , "linux-rdma@vger.kernel.org" , LKML , qemu-devel@nongnu.org Subject: Re: [PATCHv2] rdma: add a new IB_ACCESS_GIFT flag References: <20130324155153.GA8597@redhat.com> <515F3160.4020007@linux.vnet.ibm.com> <515F3948.40205@linux.vnet.ibm.com> <515F42EE.8060203@linux.vnet.ibm.com> <20130409190350.GB8212@redhat.com> <5164BFE3.4040204@linux.vnet.ibm.com> <20130410032449.GA12777@redhat.com> In-Reply-To: <20130410032449.GA12777@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13041004-3620-0000-0000-000001F80B33 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2254 Lines: 57 On 04/09/2013 11:24 PM, Michael S. Tsirkin wrote: > Which mechanism do you refer to? You patches still seem to pin each > page in guest memory at some point, which will break all COW. In > particular any pagemap tricks to detect duplicates on source that I > suggested won't work. Sorry, I mispoke. I'm reffering to dynamic server page registration. Of course it does not eliminate pinning - but it does mitigate the foot print of the VM as a feature that was requested. I have implemented it and documented it. - Michael >> On 04/09/2013 03:03 PM, Michael S. Tsirkin wrote: >>> presumably is_dup_page reads the page, so should not break COW ... >>> >>> I'm not sure about the cgroups swap limit - you might have >>> too many non COW pages so attempting to fault them all in >>> makes you exceed the limit. You really should look at >>> what is going on in the pagemap, to see if there's >>> measureable gain from the patch. >>> >>> >>> On Fri, Apr 05, 2013 at 05:32:30PM -0400, Michael R. Hines wrote: >>>> Well, I have the "is_dup_page()" commented out.......when RDMA is >>>> activated..... >>>> >>>> Is there something else in QEMU that could be touching the page that >>>> I don't know about? >>>> >>>> - Michael >>>> >>>> >>>> On 04/05/2013 05:03 PM, Roland Dreier wrote: >>>>> On Fri, Apr 5, 2013 at 1:51 PM, Michael R. Hines >>>>> wrote: >>>>>> Sorry, I was wrong. ignore the comments about cgroups. That's still broken. >>>>>> (i.e. trying to register RDMA memory while using a cgroup swap limit cause >>>>>> the process get killed). >>>>>> >>>>>> But the GIFT flag patch works (my understanding is that GIFT flag allows the >>>>>> adapter to transmit stale memory information, it does not have anything to >>>>>> do with cgroups specifically). >>>>> The point of the GIFT patch is to avoid triggering copy-on-write so >>>>> that memory doesn't blow up during migration. If that doesn't work >>>>> then there's no point to the patch. >>>>> >>>>> - R. >>>>> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/