From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40845) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eKNdc-0001av-Fz for qemu-devel@nongnu.org; Thu, 30 Nov 2017 07:08:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eKNdX-0005BZ-I9 for qemu-devel@nongnu.org; Thu, 30 Nov 2017 07:08:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6636) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eKNdX-0005AW-BY for qemu-devel@nongnu.org; Thu, 30 Nov 2017 07:08:15 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A63A64900F for ; Thu, 30 Nov 2017 12:08:14 +0000 (UTC) Date: Thu, 30 Nov 2017 12:08:06 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20171130120805.GA3952@work-vm> References: <20171129185026.23632-1-dgilbert@redhat.com> <20171130122245.7e713d2f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171130122245.7e713d2f@redhat.com> 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: Igor Mammedov Cc: qemu-devel@nongnu.org, maxime.coquelin@redhat.com, mst@redhat.com * 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. > 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