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=-6.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 60D73C4338F for ; Mon, 26 Jul 2021 01:16:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4347A6052B for ; Mon, 26 Jul 2021 01:16:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231358AbhGZAf3 (ORCPT ); Sun, 25 Jul 2021 20:35:29 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:7058 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230075AbhGZAf2 (ORCPT ); Sun, 25 Jul 2021 20:35:28 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GY20C0K9hzYgSq; Mon, 26 Jul 2021 09:10:03 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Mon, 26 Jul 2021 09:15:54 +0800 Received: from [10.174.178.91] (10.174.178.91) 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; Mon, 26 Jul 2021 09:15:54 +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> From: "yukuai (C)" Message-ID: Date: Mon, 26 Jul 2021 09:15:54 +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: <7DF40BD4-8F57-4C2E-88A9-CBC3DA2A891E@linaro.org> Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.91] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) 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 2021/07/24 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, Thanks for you advice, will do this in the next iteration. Best regards, Kuai