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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,SPF_HELO_NONE,SPF_PASS autolearn=no 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 D58E0C2D0A3 for ; Fri, 6 Nov 2020 14:19:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5ADAD20719 for ; Fri, 6 Nov 2020 14:19:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="YWzTD5Jn"; dkim=pass (1024-bit key) header.d=fb.onmicrosoft.com header.i=@fb.onmicrosoft.com header.b="YXz6hZ9d" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727204AbgKFOTq (ORCPT ); Fri, 6 Nov 2020 09:19:46 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:43806 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726939AbgKFOTp (ORCPT ); Fri, 6 Nov 2020 09:19:45 -0500 Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.42/8.16.0.42) with SMTP id 0A6EHql8004739; Fri, 6 Nov 2020 06:19:39 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : content-type : mime-version; s=facebook; bh=UAylOrWD5KY9Xh+lQo0AHKz/n1CXMq6vtBb88v/L8GI=; b=YWzTD5JnAt44EuPCH1g+ElTxLrRL6nrmjKGwNDNlO7yJVCp17fLpjwovrypVRXFb0uuM i1meQuNlJQPhhrdsUNpOh0O8fUGtz/Ol8T7SKVP7LLCTNI39xp1ivhG0ooVtWXykERYQ 0db9dALmx6DrmUw7DPuFszMIvRD7luzc1j0= Received: from mail.thefacebook.com ([163.114.132.120]) by m0089730.ppops.net with ESMTP id 34m5r19uw7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Fri, 06 Nov 2020 06:19:38 -0800 Received: from NAM04-BN3-obe.outbound.protection.outlook.com (100.104.98.9) by o365-in.thefacebook.com (100.104.94.231) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Fri, 6 Nov 2020 06:19:36 -0800 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=OKKaa6zfWmPNamiD5KBlVaYbni37tte21QW9yXE6+BFzHWXItvzzYDWoxDci+UEMdU2tDsI7KCve4IbdCToVZSoxY1vMgo9C255kz3LJZftaiD+yDK0LkVqzse0QmIv6Kin0LC8uKj/oqkzMFho6zQ0j2PlKS+iduxjwfJ3ICI/FwutCLjFOIyRagjI92q2gsDQLlC9ETApYVFe5DSMTz5IsemWVlo8GmUGHkbJtXjVLOr57rbsAKqk7WFkCPAQ6QGpjIyJuFpXgPLgReF/HyaGzFtVJzjLlmiaii08cKSxvDPH7S+wGgqHP+3cnqRk2WNFQiSkIxkH4SfY71jz2Mg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=UAylOrWD5KY9Xh+lQo0AHKz/n1CXMq6vtBb88v/L8GI=; b=CKkLpX5i4v7O7Uhb+BAW4zFzNHIiee61yMVuxMGshdPp77UoLzNt+N2x7wzxE8cOFzRu1lpkMJ3XyvUBLqbplHvud5WJIPS2GhWuuWlD+Vi+XzUZeZNzcI3qWKvUcIvtuFNPTjSHjS1wNkRbxJFmjp+NWv+c+6pFYZwjOYxjwrMlq3cUbnvODK31U5djN6Dm/S4PtEKcZdx1TyZ7evYnC85Wpp5WdLWeJRMAu7f7Yv8DLYe8qO0Qp6ZO+2TQlrsFmWH9np3DpLfJZWibzHXPN86ot+oX1A/uJUDSOf0D3VJsuwjK68yz6zY40PnFini2sYoV9a50q5SakHkDYaGapw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=fb.com; dmarc=pass action=none header.from=fb.com; dkim=pass header.d=fb.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.onmicrosoft.com; s=selector2-fb-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=UAylOrWD5KY9Xh+lQo0AHKz/n1CXMq6vtBb88v/L8GI=; b=YXz6hZ9d9M1Rjk9n1yhEHH4XwGUAhNdG4cGxA3UyQ4lwOfY0QDeiruYvqbgOcj9e+0cpH3S+VcKwatGWng1yrYkFVZAWUezdkk3XAigTgoR3e2tpTS6eH3L1Xy3idnapnMyruTbB54wzKdVJFDt74z6l+NC5cz7mZsLiRrkfspM= Authentication-Results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=fb.com; Received: from SA0PR15MB3839.namprd15.prod.outlook.com (2603:10b6:806:83::14) by SN6PR15MB2237.namprd15.prod.outlook.com (2603:10b6:805:24::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3499.29; Fri, 6 Nov 2020 14:19:34 +0000 Received: from SA0PR15MB3839.namprd15.prod.outlook.com ([fe80::988:2e42:b8ca:d347]) by SA0PR15MB3839.namprd15.prod.outlook.com ([fe80::988:2e42:b8ca:d347%9]) with mapi id 15.20.3541.021; Fri, 6 Nov 2020 14:19:34 +0000 From: "Chris Mason" To: Pavel Begunkov CC: , Josef Bacik , David Sterba , Subject: Re: [PATCH 0/4] fixes for btrfs async discards Date: Fri, 06 Nov 2020 09:19:30 -0500 X-Mailer: MailMate (1.13.2r5673) Message-ID: <0616EE84-E624-444B-AF63-7944BF484066@fb.com> In-Reply-To: <215f6406-fbe2-9eb6-2ac2-7f28b2666789@gmail.com> References: <20201105222305.GN6756@twin.jikos.cz> <215f6406-fbe2-9eb6-2ac2-7f28b2666789@gmail.com> Content-Type: text/plain; format=flowed X-Originating-IP: [172.101.208.204] X-ClientProxiedBy: CH2PR03CA0015.namprd03.prod.outlook.com (2603:10b6:610:59::25) To SA0PR15MB3839.namprd15.prod.outlook.com (2603:10b6:806:83::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.129] (172.101.208.204) by CH2PR03CA0015.namprd03.prod.outlook.com (2603:10b6:610:59::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3499.19 via Frontend Transport; Fri, 6 Nov 2020 14:19:33 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 0a830fbc-91e4-47a3-96d8-08d8825efc41 X-MS-TrafficTypeDiagnostic: SN6PR15MB2237: X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:2331; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: gZlJkUoJ6jF0vnVmF2ngGTBFAWTHjpZly/MmV+LRb6B1QP02xjCZZDuoJO1qxwI2GEuVXYQlxoYBz0YOX+KtCRC5trOIyKbe1S2Xps3fvsAvrIvPMa84uh7Inkb/FGe2KVIA532AGIRhRlB2xbslNU03tTJmpLxsZ4svoISRZeCQ4Il4yHUTqB0tgNRN3bpo9jzyX8gLWZ9nJaYy4wdASxLBrfY9xhkIzWKsts1MDgT3EpervBXvpNAtLhYLQcRng122fCBLlXp1X1Ko6NBN7pEuttAeMXO7rPWDYjSeQ+Rx+ZoGzIBX9UINrEB3eFxxC0sonpcs/W42dJPeyrPXkg== X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:SA0PR15MB3839.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFS:(136003)(376002)(346002)(396003)(366004)(39860400002)(33656002)(2906002)(316002)(16576012)(4326008)(8936002)(83380400001)(66556008)(36756003)(2616005)(6916009)(53546011)(956004)(478600001)(26005)(86362001)(54906003)(66946007)(5660300002)(186003)(52116002)(16526019)(8676002)(6486002)(66476007);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 0a830fbc-91e4-47a3-96d8-08d8825efc41 X-MS-Exchange-CrossTenant-AuthSource: SA0PR15MB3839.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Nov 2020 14:19:34.5171 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: WdS8foxBbgiHKuH4VJTkhsSbJQ4lEmF5kN/8mA4yLgCR44DuIQT9h2TcvH2qRQip X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR15MB2237 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-06_04:2020-11-05,2020-11-06 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 mlxlogscore=641 bulkscore=0 malwarescore=0 phishscore=0 mlxscore=0 clxscore=1011 impostorscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011060102 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 6 Nov 2020, at 8:20, Pavel Begunkov wrote: > On 05/11/2020 22:23, David Sterba wrote: >> On Wed, Nov 04, 2020 at 09:45:50AM +0000, Pavel Begunkov wrote: >>> Several fixes for async discards. The first patch might increase >>> discard >>> rate, drastically in some cases. That may be a suprise for those >>> assuming that hitting iops_limit is rare and rarther outliers. >>> Though, >>> it still stays in allowed range, so should be fine. >> >> I think this highly depends on the workload, if you really need to >> issue >> the discards fast because of the rate of the change in the regular >> data. >> That was the point of the async discard and the knobs, the defaults >> should be ok for most users and allow adjusting for specific loads. > > Chris mentioned that _there are_ problems with faster drives though. > The problem is that this iops_limit knot just clamps the chosen delay. > Ultimately, I want to find later a better delay function than > > delay = CONSTANT_INTERVAL_MS / nr_extents. > > But that will take some thinking. Yeah, we have drives where latencies increase as the drive fills up. Async discard moves the knee on utilization percentage before the latencies increase, but without patches like these, we do still have garbage collection related stalls. We still need to measure if the GC related stalls turn into discard-saturation stalls, but at least now we can try. -chris