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=-8.2 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 3AF1FC432C1 for ; Tue, 24 Sep 2019 10:04:10 +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 BF31A214AF for ; Tue, 24 Sep 2019 10:04:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF31A214AF 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]:43504 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iChg0-0002tN-Qs for qemu-devel@archiver.kernel.org; Tue, 24 Sep 2019 06:04:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59230) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iCheG-0001sY-CP for qemu-devel@nongnu.org; Tue, 24 Sep 2019 06:02:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iCheC-00031b-Dy for qemu-devel@nongnu.org; Tue, 24 Sep 2019 06:02:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36387) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iCheA-00030y-9k for qemu-devel@nongnu.org; Tue, 24 Sep 2019 06:02:15 -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 D8B51309E5B5; Tue, 24 Sep 2019 10:02:11 +0000 (UTC) Received: from work-vm (ovpn-117-225.ams2.redhat.com [10.36.117.225]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D719460852; Tue, 24 Sep 2019 10:02:10 +0000 (UTC) Date: Tue, 24 Sep 2019 11:02:08 +0100 From: "Dr. David Alan Gilbert" To: Wei Yang Subject: Re: [PATCH 1/3] migration/postcopy: not necessary to do discard when canonicalizing bitmap Message-ID: <20190924100208.GA2725@work-vm> References: <20190819061843.28642-1-richardw.yang@linux.intel.com> <20190819061843.28642-2-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190819061843.28642-2-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 [10.5.110.43]); Tue, 24 Sep 2019 10:02:11 +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 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: pbonzini@redhat.com, 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: > All pages, either partially sent or partially dirty, will be discarded in > postcopy_send_discard_bm_ram(), since we update the unsentmap to be > unsentmap = unsentmap | dirty in ram_postcopy_send_discard_bitmap(). > > This is not necessary to do discard when canonicalizing bitmap. And by > doing so, we separate the page discard into two individual steps: > > * canonicalize bitmap > * discard page > > Signed-off-by: Wei Yang Yes, I think when I originally wrote it, the set of pages that was discarded was different; I think it was actually the set of !unsent & dirty - i.e. only pages that had been sent and then redirtied; it later got reworked to include unsent pages as well - so this lot can be simplified. Reviewed-by: Dr. David Alan Gilbert > --- > migration/ram.c | 14 +------------- > 1 file changed, 1 insertion(+), 13 deletions(-) > > diff --git a/migration/ram.c b/migration/ram.c > index 35552c090b..075ddc468c 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -2928,7 +2928,7 @@ static int postcopy_each_ram_send_discard(MigrationState *ms) > } > > /** > - * postcopy_chunk_hostpages_pass: canocalize bitmap in hostpages > + * postcopy_chunk_hostpages_pass: canonicalize bitmap in hostpages > * > * Helper for postcopy_chunk_hostpages; it's called twice to > * canonicalize the two bitmaps, that are similar, but one is > @@ -2991,18 +2991,6 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, > host_ratio); > run_start = QEMU_ALIGN_UP(run_start, host_ratio); > > - /* Tell the destination to discard this page */ > - if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) { > - /* For the unsent_pass we: > - * discard partially sent pages > - * For the !unsent_pass (dirty) we: > - * discard partially dirty pages that were sent > - * (any partially sent pages were already discarded > - * by the previous unsent_pass) > - */ > - postcopy_discard_send_range(ms, fixup_start_addr, host_ratio); > - } > - > /* Clean up the bitmap */ > for (page = fixup_start_addr; > page < fixup_start_addr + host_ratio; page++) { > -- > 2.17.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK