From patchwork Mon Sep 21 17:30:16 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alberto Garcia X-Patchwork-Id: 1368539 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=igalia.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=igalia.com header.i=@igalia.com header.a=rsa-sha256 header.s=20170329 header.b=aLmMk7A+; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4BwBMp0yqXz9sV6 for ; Tue, 22 Sep 2020 03:32:20 +1000 (AEST) Received: from localhost ([::1]:48908 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kKPfk-0004to-FQ for incoming@patchwork.ozlabs.org; Mon, 21 Sep 2020 13:32:16 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43762) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kKPeF-0004nk-P8; Mon, 21 Sep 2020 13:30:43 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:42863) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1kKPe9-0007KW-VZ; Mon, 21 Sep 2020 13:30:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date:Subject:Cc:To:From; bh=JmcDG1B5/8OdVbH+Fhn5Lce2tHZEcej0OECmsnc39bE=; b=aLmMk7A+k/UNGcZ29MYuhaoqJkcC+mjiSwxcrJNaK91+Qls/BCUMUnq29YX7MQdg4zegHPZ0gHkyhnz6HpTY81mQ96wIcCFlRzilQ3LHmLXbpeC7i+COAJamz/Ox5PZ9tj53RgNdlETLaCR0ucdkxLv55wBpvhkqP7OybXVk/uegWDWS/mKxumiHnEj4Ft7Z5/yEdRpTZQjvmWd31UK+TIxXY2HRAKY67DKZYcRuKA/yBUkFbSTs4SdI6R6ZiprLeWN4OS6x+giYa2gU6m8EZtdBPAGnCD0dtuqHYb7PobcHMrzQIS3GCaZeypmOBV917fLgjbWU9nKlAw2HbAZBFw==; Received: from [81.0.34.134] (helo=perseus.local) by fanzine.igalia.com with esmtpsa (Cipher TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim) id 1kKPe5-0006qU-Aw; Mon, 21 Sep 2020 19:30:33 +0200 Received: from berto by perseus.local with local (Exim 4.92) (envelope-from ) id 1kKPdq-0007HJ-75; Mon, 21 Sep 2020 19:30:18 +0200 From: Alberto Garcia To: qemu-devel@nongnu.org Subject: [PATCH] docs: Document the throttle block filter Date: Mon, 21 Sep 2020 19:30:16 +0200 Message-Id: <20200921173016.27935-1-berto@igalia.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Received-SPF: pass client-ip=178.60.130.6; envelope-from=berto@igalia.com; helo=fanzine.igalia.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/21 13:30:33 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy] 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Alberto Garcia , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" This filter was added back in 2017 for QEMU 2.11 but it was never properly documented, so let's explain how it works and add a couple of examples. Signed-off-by: Alberto Garcia Reviewed-by: Kevin Wolf --- docs/throttle.txt | 107 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 106 insertions(+), 1 deletion(-) diff --git a/docs/throttle.txt b/docs/throttle.txt index cd4e109d39..c06d1b9662 100644 --- a/docs/throttle.txt +++ b/docs/throttle.txt @@ -1,6 +1,6 @@ The QEMU throttling infrastructure ================================== -Copyright (C) 2016 Igalia, S.L. +Copyright (C) 2016,2020 Igalia, S.L. Author: Alberto Garcia This work is licensed under the terms of the GNU GPL, version 2 or @@ -253,3 +253,108 @@ up. After those 60 seconds the bucket will have leaked 60 x 100 = Also, due to the way the algorithm works, longer burst can be done at a lower I/O rate, e.g. 1000 IOPS during 120 seconds. + + +The 'throttle' block filter +--------------------------- +Since QEMU 2.11 it is possible to configure the I/O limits using a +'throttle' block filter. This filter uses the exact same throttling +infrastructure described above but can be used anywhere in the node +graph, allowing for more flexibility. + +The user can create an arbitrary number of filters and each one of +them must be assigned to a group that contains the actual I/O limits. +Different filters can use the same group so the limits are shared as +described earlier in "Applying I/O limits to groups of disks". + +A group can be created using the object-add QMP function: + + { "execute": "object-add", + "arguments": { + "qom-type": "throttle-group", + "id": "group0", + "props": { + "limits" : { + "iops-total": 1000 + "bps-write": 2097152 + } + } + } + } + +throttle-group has a 'limits' property (of type ThrottleLimits as +defined in qapi/block-core.json) which can be set on creation or later +with 'qom-set'. + +A throttle-group can also be created with the -object command line +option but at the moment there is no way to pass a 'limits' parameter +that contains a ThrottleLimits structure. The solution is to set the +individual values directly, like in this example: + + -object throttle-group,id=group0,x-iops-total=1000,x-bps-write=2097152 + +Note however that this not stable API (hence the 'x-' prefixes) and +can change or disappear in the future. + +Once we have a throttle-group we can use the throttle block filter, +where the 'file' property must be set to the block device that we want +to filter: + + { "execute": "blockdev-add", + "arguments": { + "options": { + "driver": "qcow2", + "node-name": "disk0", + "file": { + "driver": "file", + "filename": "/path/to/disk.qcow2" + } + } + } + } + + { "execute": "blockdev-add", + "arguments": { + "driver": "throttle", + "node-name": "throttle0", + "throttle-group": "group0", + "file": "disk0" + } + } + +A similar setup can also be done with the command line, for example: + + -drive driver=throttle,throttle-group=group0, + file.driver=qcow2,file.file.filename=/path/to/disk.qcow2 + +The scenario described so far is very simple but the throttle block +filter allows for more complex configurations. For example, let's say +that we have three different drives and we want to set I/O limits for +each one of them and an additional set of limits for the combined I/O +of all three drives. + +First we would define all throttle groups, one for each one of the +drives and one that would apply to all of them: + + -object throttle-group,id=limits0,x-iops-total=2000 + -object throttle-group,id=limits1,x-iops-total=2500 + -object throttle-group,id=limits2,x-iops-total=3000 + -object throttle-group,id=limits012,x-iops-total=4000 + +Now we can define the drives, and for each one of them we use two +chained throttle filters: the drive's own filter and the combined +filter. + + -drive driver=throttle,throttle-group=limits012, + file.driver=throttle,file.throttle-group=limits0 + file.file.driver=qcow2,file.file.file.filename=/path/to/disk0.qcow2 + -drive driver=throttle,throttle-group=limits012, + file.driver=throttle,file.throttle-group=limits1 + file.file.driver=qcow2,file.file.file.filename=/path/to/disk1.qcow2 + -drive driver=throttle,throttle-group=limits012, + file.driver=throttle,file.throttle-group=limits2 + file.file.driver=qcow2,file.file.file.filename=/path/to/disk2.qcow2 + +In this example the individual drives have IOPS limits of 2000, 2500 +and 3000 respectively but the total combined I/O can never exceed 4000 +IOPS.