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 9F8BDC6FD1C for ; Fri, 24 Mar 2023 15:45:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pficl-00075S-30; Fri, 24 Mar 2023 10:42:35 -0400 Received: from [2001:470:142:3::10] (helo=eggs.gnu.org) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pfici-00074Y-22 for qemu-devel@nongnu.org; Fri, 24 Mar 2023 10:42:33 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pficf-0001nn-Uo for qemu-devel@nongnu.org; Fri, 24 Mar 2023 10:42:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679668949; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kIsEADNHy/tHejPpYRCJm0gN+A4OBq8ebw+apHpT83o=; b=hN9dkJp3Qzsqh/JwzVJtiC6d3yM4dV1+5BbYRBJIk+ajSPOkP1epjjVpyLzn7Iva8MuBxc 3wD8+wsiwLPtZoSyhEDl17nG1CBX4cIovPTQTd+9C33MfL7Xuc9IzqFUpImreoXE6U8Vjk sI0zA40JW3/ZlqtHQsnGnsJTvtqzZCc= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-349-zYjErsdNN1yYRHZrd0Su8g-1; Fri, 24 Mar 2023 10:42:27 -0400 X-MC-Unique: zYjErsdNN1yYRHZrd0Su8g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4B1C6100DEAC for ; Fri, 24 Mar 2023 14:42:27 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2ACC02166B29 for ; Fri, 24 Mar 2023 14:42:27 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 5B06121E692C; Fri, 24 Mar 2023 15:32:28 +0100 (CET) From: Markus Armbruster To: Hyman Huang Cc: qemu-devel , Peter Xu , "Dr. David Alan Gilbert" , Juan Quintela , Thomas Huth , Paolo Bonzini , Eric Blake , Peter Maydell , Richard Henderson Subject: Re: [PATCH v4 06/10] migration: Introduce dirty-limit capability References: <871qlepcw7.fsf@pond.sub.org> Date: Fri, 24 Mar 2023 15:32:28 +0100 In-Reply-To: (Hyman Huang's message of "Fri, 24 Mar 2023 20:47:50 +0800") Message-ID: <87ttyamd8j.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hyman Huang writes: > =E5=9C=A8 2023/3/24 20:11, Markus Armbruster =E5=86=99=E9=81=93: >> huangy81@chinatelecom.cn writes: >>=20 >>> From: Hyman Huang(=E9=BB=84=E5=8B=87) >>> >>> Introduce migration dirty-limit capability, which can >>> be turned on before live migration and limit dirty >>> page rate durty live migration. >>> >>> Introduce migrate_dirty_limit function to help check >>> if dirty-limit capability enabled during live migration. >>> >>> Meanwhile, refactor vcpu_dirty_rate_stat_collect >>> so that period can be configured instead of hardcoded. >>> >>> dirty-limit capability is kind of like auto-converge >>> but using dirty limit instead of traditional cpu-throttle >>> to throttle guest down. To enable this feature, turn on >>> the dirty-limit capability before live migration using >>> migrate-set-capabilities, and set the parameters >>> "x-vcpu-dirty-limit-period", "vcpu-dirty-limit" suitably >>> to speed up convergence. >>> >>> Signed-off-by: Hyman Huang(=E9=BB=84=E5=8B=87) >>> Acked-by: Peter Xu >> [...] >>=20 >>> diff --git a/qapi/migration.json b/qapi/migration.json >>> index d33cc2d582..b7a92be055 100644 >>> --- a/qapi/migration.json >>> +++ b/qapi/migration.json >>> @@ -477,6 +477,8 @@ >>> # will be handled faster. This is a performance f= eature and >>> # should not affect the correctness of postcopy mi= gration. >>> # (since 7.1) >>> +# @dirty-limit: Use dirty-limit to throttle down guest if enabled. >>> +# (since 8.0) >> >> Feels too terse. What exactly is used and how? It's not the capability >> itself (although the text sure sounds like it). I guess it's the thing >> you set with command set-vcpu-dirty-limit. >> >> Is that used only when the capability is set? > > Yes, live migration set "dirty-limit" value when that capability is set, > the comment changes to "Apply the algorithm of dirty page rate limit to t= hrottle down guest if capability is set, rather than auto-converge". > > Please continue to polish the doc if needed. Thanks. Let's see whether I understand. Throttling happens only during migration. There are two throttling algorithms: "auto-converge" (default) and "dirty page rate limit". The latter can be tuned with set-vcpu-dirty-limit. Correct? What happens when migration capability dirty-limit is enabled, but the user hasn't set a limit with set-vcpu-dirty-limit, or canceled it with cancel-vcpu-dirty-limit? >>> # >>> # Features: >>> # @unstable: Members @x-colo and @x-ignore-shared are experimental. >>> @@ -492,7 +494,7 @@ >>> 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activat= e', >>> { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, >>> 'validate-uuid', 'background-snapshot', >>> - 'zero-copy-send', 'postcopy-preempt'] } >>> + 'zero-copy-send', 'postcopy-preempt', 'dirty-limit'] } >>> ## >>> # @MigrationCapabilityStatus: >> [...] >>=20