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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 5E676C432BE for ; Tue, 3 Aug 2021 11:30:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FBAC60EBC for ; Tue, 3 Aug 2021 11:30:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235537AbhHCLay (ORCPT ); Tue, 3 Aug 2021 07:30:54 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:12440 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235426AbhHCLax (ORCPT ); Tue, 3 Aug 2021 07:30:53 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GfCJW70cgzckR6; Tue, 3 Aug 2021 19:27:07 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Tue, 3 Aug 2021 19:30:41 +0800 Received: from [10.174.176.73] (10.174.176.73) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 3 Aug 2021 19:30:40 +0800 Subject: Re: [PATCH 1/3] block, bfq: do not idle if only one cgroup is activated To: Paolo Valente CC: Jens Axboe , , , References: <20210714094529.758808-1-yukuai3@huawei.com> <20210714094529.758808-2-yukuai3@huawei.com> <7DF40BD4-8F57-4C2E-88A9-CBC3DA2A891E@linaro.org> <8D4774E6-0DEB-4DC4-B28B-13F5A933E12F@linaro.org> From: "yukuai (C)" Message-ID: <1fe2b6cb-d770-d53f-2a17-fdce480d7be0@huawei.com> Date: Tue, 3 Aug 2021 19:30:40 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <8D4774E6-0DEB-4DC4-B28B-13F5A933E12F@linaro.org> Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.73] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/08/03 15:07, Paolo Valente wrote: > > >> Il giorno 31 lug 2021, alle ore 09:10, yukuai (C) ha scritto: >> >> On 2021/07/24 15:12, Paolo Valente wrote: >>>> Il giorno 14 lug 2021, alle ore 11:45, Yu Kuai ha scritto: >>>> >>>> If only one group is activated, specifically >>>> 'bfqd->num_groups_with_pending_reqs == 1', there is no need to guarantee >>>> the same share of the throughput of queues in the same group. >>>> >>>> Thus change the condition from '> 0' to '> 1' in >>>> bfq_asymmetric_scenario(). >>> I see your point, and I agree with your goal. Yet, your change seems >>> not to suffer from the following problem. >>> In addition to the groups that are created explicitly, there is the >>> implicit root group. So, when bfqd->num_groups_with_pending_reqs == >>> 1, there may be both active processes in the root group and active >>> processes in the only group created explicitly. In this case, idling >>> is needed to preserve service guarantees. >>> Probably your idea should be improved by making sure that there is >>> pending I/O only from either the root group or the explicit group. >>> Thanks, >>> Paolo >> >> >> Hi, Paolo >> > > Hi > >> I'm trying to add support to judge if root group have pending rqs, the >> implementation involve setting and clearing the busy state. >> > > I wouldn't use the busy state, as it does not take in-flight requests > into account. For I/O control, the latter are as important as the > ones still queued in the scheduler. For this reason, I take in-flight > requests into account when counting > bfqd->num_groups_with_pending_reqs. > > See, e.g., this > > if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) { > ... > bfq_weights_tree_remove(bfqd, bfqq); > } > > in bfq_completed_request. > > I would replicate the same logic in deciding whether the root group > has pending I/O. > Hi, Paolo Thanks for your advice, I'll send a new patchset soon. Kuai