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=-7.2 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 4B32DC433F5 for ; Tue, 14 Sep 2021 12:35:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 366EC6103B for ; Tue, 14 Sep 2021 12:35:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232801AbhINMgt (ORCPT ); Tue, 14 Sep 2021 08:36:49 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:9868 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232702AbhINMgs (ORCPT ); Tue, 14 Sep 2021 08:36:48 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4H82kv1KkBz8yWP; Tue, 14 Sep 2021 20:31:03 +0800 (CST) Received: from dggema772-chm.china.huawei.com (10.1.198.214) 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 15.1.2308.8; Tue, 14 Sep 2021 20:35:28 +0800 Received: from [127.0.0.1] (10.69.38.196) by dggema772-chm.china.huawei.com (10.1.198.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.8; Tue, 14 Sep 2021 20:35:28 +0800 Subject: Re: [RFC] Perfomance varies according to sysctl_sched_migration_cost To: Peter Zijlstra CC: , , , , , , , , <21cnbao@gmail.com>, "Linux Kernel Mailing List" , "Song Bao Hua (Barry Song)" , , "guodong.xu@linaro.org" References: From: Yicong Yang Message-ID: <5be9d830-d6f4-6c2e-278f-940baeb57d89@hisilicon.com> Date: Tue, 14 Sep 2021 20:35:28 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.69.38.196] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggema772-chm.china.huawei.com (10.1.198.214) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/9/14 19:30, Peter Zijlstra wrote: > On Tue, Sep 14, 2021 at 03:27:09PM +0800, Yicong Yang wrote: >> 2. The ABI now has been removed from sysctl and moved to debugfs. As tuning this can improve the performance >> of some workloads on some platforms, maybe it's better to make it a formal sysctl again with docs? > > It never was an ABI, there is nothing to restore. It has always been > CONFIG_SCHED_DEBUG. > It's right that CONIG_SCHED_DEBUG is on for most releases and it's same to tune it through debugfs. So I'm not with a strong heart to restore it but just curious about this magic value since it does have some influence when tuning this on my platform. > I'm open to topology based improvements to the code, but I don't think > user tunables are a good way. > sure, it's better to make the scheduler topology adapted rather than manually tuned, but certainly it's not that easy to achieve. Maybe I can investigate the whole story first, seems we didn't use a constant migration_cost_ns at very beginning, to see if there's any inspiration. Thanks. > . >