From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43305) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UQK2n-00074g-5q for qemu-devel@nongnu.org; Thu, 11 Apr 2013 12:08:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UQK2j-0002pC-07 for qemu-devel@nongnu.org; Thu, 11 Apr 2013 12:08:12 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:35806) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UQK2i-0002p4-Rr for qemu-devel@nongnu.org; Thu, 11 Apr 2013 12:08:08 -0400 Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 11 Apr 2013 12:08:08 -0400 Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id DC23F6E82AD for ; Thu, 11 Apr 2013 12:07:11 -0400 (EDT) Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r3BG7DRk26280026 for ; Thu, 11 Apr 2013 12:07:14 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r3BG6NFT006380 for ; Thu, 11 Apr 2013 13:06:24 -0300 Message-ID: <5166DF7A.6050909@linux.vnet.ibm.com> Date: Thu, 11 Apr 2013 12:06:18 -0400 From: "Michael R. Hines" MIME-Version: 1.0 References: <5165C60E.20006@linux.vnet.ibm.com> <20130411071927.GA17063@redhat.com> <5166B6B1.2030003@linux.vnet.ibm.com> <20130411134820.GA24942@redhat.com> <5166C19A.1040402@linux.vnet.ibm.com> <20130411143718.GC24942@redhat.com> <5166D460.2070106@linux.vnet.ibm.com> <5166D7D5.8080403@redhat.com> <20130411154639.GC22779@redhat.com> <5166DB29.5040101@redhat.com> <20130411155811.GA22992@redhat.com> In-Reply-To: <20130411155811.GA22992@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH RDMA support v5: 03/12] comprehensive protocol documentation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org, owasserm@redhat.com, abali@us.ibm.com, mrhines@us.ibm.com, gokul@us.ibm.com, Paolo Bonzini On 04/11/2013 11:58 AM, Michael S. Tsirkin wrote: > On Thu, Apr 11, 2013 at 05:47:53PM +0200, Paolo Bonzini wrote: >> Il 11/04/2013 17:46, Michael S. Tsirkin ha scritto: >>>> Ok, let's keep it simple. The only two things we need are: >>>> >>>> 1) remove the patch to disable is_dup_page >>>> >>>> 2) rename the transport to "x-rdma" (just in migration.c) >>>> >>>> Both things together let us keep it safe for a release or two. Let's >>>> merge this thing. >>> I would drop the chunk based thing too. Besides being slow, it turns >>> out that it pins all memory anyway. So no memory overcommit. >> It doesn't pin zero pages. Those are never transmitted (it's a recent >> change). So pages that are ballooned at the beginning of migration, and >> remain ballooned throughout, will never be pinned. >> >> Paolo > Of course Michael says it's slow unless you disable zero page detection, > and then I'm guessing it does? > Only during the bulk phase round, and even then, as Paolo described, zero pages do not get pinned on the destination. Chunk registration is still very valuable when zero page detection is activated. The realization is that chunk registration (and zero page scanning) have very little effect whatsoever on performance *after* the bulk phase round because pages have already been mapped and already pinned in memory for life. - Michael