From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49590) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eKO9P-0000Tm-CL for qemu-devel@nongnu.org; Thu, 30 Nov 2017 07:41:12 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eKO9L-0003Rx-9b for qemu-devel@nongnu.org; Thu, 30 Nov 2017 07:41:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60406) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eKO9L-0003Qn-1Q for qemu-devel@nongnu.org; Thu, 30 Nov 2017 07:41:07 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 351D180099 for ; Thu, 30 Nov 2017 12:41:06 +0000 (UTC) Date: Thu, 30 Nov 2017 13:40:57 +0100 From: Igor Mammedov Message-ID: <20171130134057.1d8ecc3e@redhat.com> In-Reply-To: <20171130120805.GA3952@work-vm> References: <20171129185026.23632-1-dgilbert@redhat.com> <20171130122245.7e713d2f@redhat.com> <20171130120805.GA3952@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC 0/7] Rework vhost memory region updates List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, maxime.coquelin@redhat.com, mst@redhat.com On Thu, 30 Nov 2017 12:08:06 +0000 "Dr. David Alan Gilbert" wrote: > * Igor Mammedov (imammedo@redhat.com) wrote: > > On Wed, 29 Nov 2017 18:50:19 +0000 > > "Dr. David Alan Gilbert (git)" wrote: > > > > > From: "Dr. David Alan Gilbert" > > > > > > Hi, > > > This is an experimental set that reworks the way the vhost > > > code handles changes in physical address space layout that > > > came from a discussion with Igor. > > Thanks for looking into it. > > > > > > > Instead of updating and trying to merge sections of address > > > space on each add/remove callback, we wait until the commit phase > > > and go through and rebuild a list by walking the Flatview of > > > memory and end up producing an ordered list. > > > We compare the list to the old list to trigger updates. > > > > > > Note, only very lightly tested so far, I'm just trying to see if it's > > > the right shape. > > > > > > Igor, is this what you were intending? > > > > I was thinking about a little less intrusive approach > > > > where vhost_region_add/del are modified to maintain > > sorted by GPA array of mem_sections, vhost_dev::mem is dropped > > altogether and vhost_memory_region array is build/used/freed > > on every vhost_commit(). > > Maintaining sorted array should roughly cost us O(2 log n) if > > binary search is used. > > > > However I like your idea with iterator even more as it have > > potential to make it even faster O(n) if we get rid of > > quadratic and relatively complex vhost_update_compare_list(). > > Note vhost_update_compare_list is complex, > but it is O(n) - it's > got nested loops, but the inner loop moves forward and oldi never > gets reset back to zero. While skimming through patches I've overlooked it. Anyways, why memcmp(old_arr, new_arr) is not sufficient to detect a change in memory map? > > > Pls, see comments on individual patches. > > Thanks; I have fixed a couple of bugs since I posted, so I'm > more interested in structure/shape. Any good ideas how to test > it are welcome. > > Dave > > > > > > Dave > > > > > > Dr. David Alan Gilbert (7): > > > memory: address_space_iterate > > > vhost: Move log_dirty check > > > vhost: New memory update functions > > > vhost: update_mem_cb implementation > > > vhost: Compare new and old memory lists > > > vhost: Copy updated region data into device state > > > vhost: Remove vhost_set_memory and children > > > > > > hw/virtio/trace-events | 8 + > > > hw/virtio/vhost.c | 424 ++++++++++++++++++++++--------------------------- > > > include/exec/memory.h | 23 +++ > > > memory.c | 22 +++ > > > 4 files changed, 241 insertions(+), 236 deletions(-) > > > > > > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK