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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id C92BEC433EF for ; Mon, 4 Jul 2022 09:08:07 +0000 (UTC) Received: from localhost ([::1]:55684 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o8I3q-00059Z-Mc for qemu-devel@archiver.kernel.org; Mon, 04 Jul 2022 05:08:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37528) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o8I2Z-0004E5-U0 for qemu-devel@nongnu.org; Mon, 04 Jul 2022 05:06:47 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:38360) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o8I2W-00017x-B0 for qemu-devel@nongnu.org; Mon, 04 Jul 2022 05:06:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656925603; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=cz+q/HFFKDNVFL5MRIyx+eFeOnPBtdYySp3CTyCinL8=; b=c7P5trBx1xLIOgG/6YpNlfg/sd5gW7YFC4aDR2FfNKwcIAaFOegFXGJmWO7uzqsM+8DQM1 H8UMAAolCu1Eudmgx38o+CLu6FPwlp5pW073pG0kucXhl9fLvCmCvYK9RmvsYf2zyg7rOT XRhxmHDiG1t4Dma86xiZ+Py/DIL7yH0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-214-Igcmkys5MKiO0yOw7GS8cw-1; Mon, 04 Jul 2022 05:06:39 -0400 X-MC-Unique: Igcmkys5MKiO0yOw7GS8cw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7B6C52999B47 for ; Mon, 4 Jul 2022 09:06:39 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.151]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1A89418EB7; Mon, 4 Jul 2022 09:06:37 +0000 (UTC) Date: Mon, 4 Jul 2022 10:06:35 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: Leonardo Bras , Juan Quintela , "Dr. David Alan Gilbert" , Eric Blake , Peter Xu , qemu-devel@nongnu.org Subject: Re: [PATCH v2 2/3] Add zero-copy-copied migration stat Message-ID: References: <20220701155935.482503-1-leobras@redhat.com> <20220701155935.482503-3-leobras@redhat.com> <877d4tz9gx.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <877d4tz9gx.fsf@pond.sub.org> User-Agent: Mutt/2.2.6 (2022-06-05) X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Jul 04, 2022 at 08:18:54AM +0200, Markus Armbruster wrote: > Leonardo Bras writes: > > > Signed-off-by: Leonardo Bras > > --- > > qapi/migration.json | 5 ++++- > > migration/migration.c | 1 + > > monitor/hmp-cmds.c | 4 ++++ > > 3 files changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/qapi/migration.json b/qapi/migration.json > > index 7102e474a6..925f009868 100644 > > --- a/qapi/migration.json > > +++ b/qapi/migration.json > > @@ -55,6 +55,9 @@ > > # @postcopy-bytes: The number of bytes sent during the post-copy phase > > # (since 7.0). > > # > > +# @zero-copy-copied: The number of zero-copy flushes that reported data sent > > +# using zero-copy that ended up being copied. (since 7.2) > > The description feels awkward. What's a "zero-copy flush", and why > should the user care? I figure what users care about is the number of > all-zero pages we had to "copy", i.e. send the bulky way. Is this what > @zero-copy-copied reports? MigrationCapability field @zero-copy-send instructs QEMU to try to avoid copying data between userspace and kernel space when transmitting RAM region. Even if the kernel supports zero copy, it is not guaranteed to happen, it is merely a request to try. QEMU periodically (once per migration iteration) flushes outstanding zero-copy requests and gets an indication back of whether any copies took place or not. So this counter is a reflection of how many iterations resulted in zero-copy not being fully honoured. IOW, ideally this counter will always be zero. If it is non-zero, then the magnitude gives a very very very rough guide to what's going on. If it is '1' then it was just a transient limitation. If it matches the number of migration iterations, then it is a more systemic limitation. Incidentally, do we report the migration iteration count ? I thought we did, but i'm not finding it now that I look. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|