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, URIBL_BLOCKED,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 DEB38ECE58C for ; Fri, 11 Oct 2019 10:16:10 +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 B2C212084C for ; Fri, 11 Oct 2019 10:16:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2C212084C 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]:48106 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iIrxx-0000y5-Tv for qemu-devel@archiver.kernel.org; Fri, 11 Oct 2019 06:16:09 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33536) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iIrxI-0000ZM-1H for qemu-devel@nongnu.org; Fri, 11 Oct 2019 06:15:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iIrxG-0004iT-NO for qemu-devel@nongnu.org; Fri, 11 Oct 2019 06:15:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46626) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iIrxG-0004i8-Ej for qemu-devel@nongnu.org; Fri, 11 Oct 2019 06:15:26 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7EDD9317528A; Fri, 11 Oct 2019 10:15:25 +0000 (UTC) Received: from work-vm (ovpn-117-210.ams2.redhat.com [10.36.117.210]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6E5F53CC8; Fri, 11 Oct 2019 10:15:24 +0000 (UTC) Date: Fri, 11 Oct 2019 11:15:22 +0100 From: "Dr. David Alan Gilbert" To: Wei Yang Subject: Re: [PATCH 2/2] migration/postcopy: map large zero page in postcopy_ram_incoming_setup() Message-ID: <20191011101522.GN3354@work-vm> References: <20191005135021.21721-1-richardw.yang@linux.intel.com> <20191005135021.21721-3-richardw.yang@linux.intel.com> <20191008172423.GH3441@work-vm> <20191009011048.GD26203@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191009011048.GD26203@richard> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Fri, 11 Oct 2019 10:15:25 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] 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: 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: > On Tue, Oct 08, 2019 at 06:24:23PM +0100, Dr. David Alan Gilbert wrote: > >* Wei Yang (richardw.yang@linux.intel.com) wrote: > >> postcopy_ram_incoming_setup() and postcopy_ram_incoming_cleanup() are > >> counterpart. It is reasonable to map/unmap large zero page in these two > >> functions respectively. > >> > >> Signed-off-by: Wei Yang > > > >Yes, OK. > > > >> --- > >> migration/postcopy-ram.c | 34 +++++++++++++++++----------------- > >> 1 file changed, 17 insertions(+), 17 deletions(-) > >> > >> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > >> index e554f93eec..813cfa5c42 100644 > >> --- a/migration/postcopy-ram.c > >> +++ b/migration/postcopy-ram.c > >> @@ -1142,6 +1142,22 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis) > >> return -1; > >> } > >> > >> + /* > >> + * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for hugepages > >> + */ > >> + mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, > >> + PROT_READ | PROT_WRITE, > >> + MAP_PRIVATE | MAP_ANONYMOUS, > >> + -1, 0); > >> + if (mis->postcopy_tmp_zero_page == MAP_FAILED) { > >> + int e = errno; > >> + mis->postcopy_tmp_zero_page = NULL; > >> + error_report("%s: Failed to map large zero page %s", > >> + __func__, strerror(e)); > >> + return -e; > > > >Note this starts returning -errno where the rest of this function > >returns 0 or -1; returning -errno is a good thing I think and it might > >be good to change the other returns. > > > > This is reasonable, while I am thinking how caller would handle this. > > For example, the return value would be finally returned to > qemu_loadvm_state_main(). If we handle each errno respectively in this > function, the code would be difficult to read and maintain. > > Would it be good to classify return value to different category? Like > > POSTCOPY_FATAL > POSTCOPY_RETRY > POSTCOPY_DISABLE It's actually quite difficult because unix errno's are too simple; an EIO has too many causes. ideally we'd like to be able to separate out a network transport error that occurs during the postcopy phase for recovery and make sure that we don't confuse that with any other error. Dave > > > > >Reviewed-by: Dr. David Alan Gilbert > > > >> + } > >> + memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); > >> + > >> /* > >> * Ballooning can mark pages as absent while we're postcopying > >> * that would cause false userfaults. > >> @@ -1248,23 +1264,7 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, > >> qemu_ram_block_host_offset(rb, > >> host)); > >> } else { > >> - /* The kernel can't use UFFDIO_ZEROPAGE for hugepages */ > >> - if (!mis->postcopy_tmp_zero_page) { > >> - mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, > >> - PROT_READ | PROT_WRITE, > >> - MAP_PRIVATE | MAP_ANONYMOUS, > >> - -1, 0); > >> - if (mis->postcopy_tmp_zero_page == MAP_FAILED) { > >> - int e = errno; > >> - mis->postcopy_tmp_zero_page = NULL; > >> - error_report("%s: %s mapping large zero page", > >> - __func__, strerror(e)); > >> - return -e; > >> - } > >> - memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); > >> - } > >> - return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, > >> - rb); > >> + return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, rb); > >> } > >> } > >> > >> -- > >> 2.17.1 > >> > >-- > >Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > -- > Wei Yang > Help you, Help me -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK