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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 EE56FC74A28 for ; Wed, 10 Jul 2019 14:24:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C2F1D20651 for ; Wed, 10 Jul 2019 14:24:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="pVHBABQl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727847AbfGJOYV (ORCPT ); Wed, 10 Jul 2019 10:24:21 -0400 Received: from forwardcorp1j.mail.yandex.net ([5.45.199.163]:59424 "EHLO forwardcorp1j.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbfGJOYV (ORCPT ); Wed, 10 Jul 2019 10:24:21 -0400 Received: from mxbackcorp1g.mail.yandex.net (mxbackcorp1g.mail.yandex.net [IPv6:2a02:6b8:0:1402::301]) by forwardcorp1j.mail.yandex.net (Yandex) with ESMTP id 84F472E148C; Wed, 10 Jul 2019 17:24:17 +0300 (MSK) Received: from smtpcorp1p.mail.yandex.net (smtpcorp1p.mail.yandex.net [2a02:6b8:0:1472:2741:0:8b6:10]) by mxbackcorp1g.mail.yandex.net (nwsmtp/Yandex) with ESMTP id P99c9oXlfq-OGtaLe0V; Wed, 10 Jul 2019 17:24:17 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1562768657; bh=uyHdLmnNK6wDjc0FbiZHSr4crktRu3Qh+meXtiizJCA=; h=In-Reply-To:Message-ID:From:Date:References:To:Subject:Cc; b=pVHBABQlzV1NxxP+TDNxdXd1oAjFvsQubsq0/n8lPjX7gYejh2cdj9CGgt87MAY6s oV89O1eIFr9zBpXb+vmGuEaQ/JhiseBjUArrxtZha1U1f24xbfMEXZUj9hivWwmsgX aOBxGayo32RadXonR90WJBUiMFD2Im4fEaqsOwXY= Authentication-Results: mxbackcorp1g.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-red.dhcp.yndx.net (dynamic-red.dhcp.yndx.net [2a02:6b8:0:40c:fce8:911:2fe8:4dfb]) by smtpcorp1p.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id wy86eJmWtT-OGw4BaM7; Wed, 10 Jul 2019 17:24:16 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: Re: [PATCH] blk-throttle: fix zero wait time for iops throttled group To: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Liu Bo , stable@vger.kernel.org References: <156259979778.2486.6296077059654653057.stgit@buzz> <30caacb5-4d45-016b-a97d-db8b37010218@kernel.dk> From: Konstantin Khlebnikov Message-ID: Date: Wed, 10 Jul 2019 17:24:16 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <30caacb5-4d45-016b-a97d-db8b37010218@kernel.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10.07.2019 17:00, Jens Axboe wrote: > On 7/8/19 9:29 AM, Konstantin Khlebnikov wrote: >> After commit 991f61fe7e1d ("Blk-throttle: reduce tail io latency when iops >> limit is enforced") wait time could be zero even if group is throttled and >> cannot issue requests right now. As a result throtl_select_dispatch() turns >> into busy-loop under irq-safe queue spinlock. >> >> Fix is simple: always round up target time to the next throttle slice. > > Applied, thanks. In the future, please break lines at 72 chars in > commit messages, I fixed it up. > Ok, but Documentation/process/submitting-patches.rst and scripts/checkpatch.pl recommends 75 chars per line.