From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9021AC31E40 for ; Tue, 6 Aug 2019 14:51:56 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 64EFF2070D for ; Tue, 6 Aug 2019 14:51:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 64EFF2070D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33916 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hv0od-0005wN-8r for qemu-devel@archiver.kernel.org; Tue, 06 Aug 2019 10:51:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46953) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hv0o6-0005Wa-NB for qemu-devel@nongnu.org; Tue, 06 Aug 2019 10:51:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hv0o5-000204-Jq for qemu-devel@nongnu.org; Tue, 06 Aug 2019 10:51:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51924) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hv0o5-0001zh-Bt for qemu-devel@nongnu.org; Tue, 06 Aug 2019 10:51:21 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8DEDA31D8AC; Tue, 6 Aug 2019 14:51:20 +0000 (UTC) Received: from work-vm (ovpn-117-206.ams2.redhat.com [10.36.117.206]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 98C0A60A35; Tue, 6 Aug 2019 14:51:19 +0000 (UTC) Date: Tue, 6 Aug 2019 15:51:17 +0100 From: "Dr. David Alan Gilbert" To: Wei Yang Message-ID: <20190806145117.GF3066@work-vm> References: <20190806004648.8659-1-richardw.yang@linux.intel.com> <20190806004648.8659-2-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20190806004648.8659-2-richardw.yang@linux.intel.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 06 Aug 2019 14:51:20 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 1/2] migration/postcopy: simplify calculation of run_start and fixup_start_addr X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Wei Yang (richardw.yang@linux.intel.com) wrote: > The purpose of the calculation is to find a HostPage which is partially > dirty. >=20 > * fixup_start_addr points to the start of the HostPage to discard > * run_start points to the next HostPage to check >=20 > While in the middle stage, there would two cases for run_start: >=20 > * aligned with HostPage means this is not partially dirty > * not aligned means this is partially dirty >=20 > When it is aligned, no work and calculation is necessary. run_start > already points to the start of next HostPage and is ready to continue. >=20 > When it is not aligned, the calculation could be simplified with: >=20 > * fixup_start_addr =3D QEMU_ALIGN_DOWN(run_start, host_ratio) > * run_start =3D QEMU_ALIGN_UP(run_start, host_ratio) >=20 > By doing so, run_start always points to the next HostPage to check. > fixup_start_addr always points to the HostPage to discard. >=20 > Signed-off-by: Wei Yang Yes that's a lot shorter; note it doess it on top of your cleanup =66rom a couple of weeks back. Reviewed-by: Dr. David Alan Gilbert > --- > migration/ram.c | 34 +++++++--------------------------- > 1 file changed, 7 insertions(+), 27 deletions(-) >=20 > diff --git a/migration/ram.c b/migration/ram.c > index c9585487ac..d86661a015 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -2956,7 +2956,6 @@ static void postcopy_chunk_hostpages_pass(Migration= State *ms, bool unsent_pass, > } > =20 > while (run_start < pages) { > - unsigned long fixup_start_addr; > unsigned long host_offset; > =20 > /* > @@ -2964,45 +2963,26 @@ static void postcopy_chunk_hostpages_pass(Migrati= onState *ms, bool unsent_pass, > * page, then we need to fixup this host page. > */ > host_offset =3D run_start % host_ratio; > - if (host_offset) { > - fixup_start_addr =3D run_start - host_offset; > - /* > - * This host page has gone, the next loop iteration starts > - * from after the fixup > - */ > - run_start =3D fixup_start_addr + host_ratio; > - } else { > + if (!host_offset) { > /* Find the end of this run */ > - unsigned long run_end; > if (unsent_pass) { > - run_end =3D find_next_bit(unsentmap, pages, run_start + = 1); > + run_start =3D find_next_bit(unsentmap, pages, run_start = + 1); > } else { > - run_end =3D find_next_zero_bit(bitmap, pages, run_start = + 1); > + run_start =3D find_next_zero_bit(bitmap, pages, run_star= t + 1); > } > /* > * If the end isn't at the start of a host page, then the > * run doesn't finish at the end of a host page > * and we need to discard. > */ > - host_offset =3D run_end % host_ratio; > - if (host_offset) { > - fixup_start_addr =3D run_end - host_offset; > - /* > - * This host page has gone, the next loop iteration star= ts > - * from after the fixup > - */ > - run_start =3D fixup_start_addr + host_ratio; > - } else { > - /* > - * No discards on this iteration, next loop starts from > - * next sent/dirty page > - */ > - run_start =3D run_end + 1; > - } > + host_offset =3D run_start % host_ratio; > } > =20 > if (host_offset) { > unsigned long page; > + unsigned long fixup_start_addr =3D QEMU_ALIGN_DOWN(run_start, > + host_ratio); > + run_start =3D QEMU_ALIGN_UP(run_start, host_ratio); > =20 > /* Tell the destination to discard this page */ > if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) { > --=20 > 2.17.1 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK