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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 D05B8C433E2 for ; Thu, 25 Mar 2021 22:02:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FC8361924 for ; Thu, 25 Mar 2021 22:02:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231144AbhCYV7m (ORCPT ); Thu, 25 Mar 2021 17:59:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230461AbhCYV7F (ORCPT ); Thu, 25 Mar 2021 17:59:05 -0400 Received: from mail-qt1-x835.google.com (mail-qt1-x835.google.com [IPv6:2607:f8b0:4864:20::835]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1330C06174A for ; Thu, 25 Mar 2021 14:59:04 -0700 (PDT) Received: by mail-qt1-x835.google.com with SMTP id l13so2890921qtu.9 for ; Thu, 25 Mar 2021 14:59:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8cwwbYqI+w00egCRCaNukq5DD3eWu7cnLa6VwLpjfl8=; b=iemGxUmO/N4+jYKKQX84i4qZHfAOjZ0sMxwEel3eFqXs0Le6ITeV/cBJkmMSijBW2Z SFZiF2c1K8SuXOa3Qi6l3FJqOcitfGQy7fSOPr04QhCcBGtOsX9e4qSTptdt/gbUxIJk oW5NHHV0nMxRaarldrMeEo8dRLYlryB2JZNTsxNCRLaJ4qpp5vAjMSt3fanGqtWP4pYq cdrc47Nerpk59SO3uM8OzvBMZrJwGo9LwBa3K4nEZAacJs+Uzc7iDMsAY4iaEw90rrtN SlTnny6qvBpkNv3UFeBVtepTAUIhtcn2tFMk6/Z4Mu8VD3BVFlg6DU8W0MPViCPLOrfW bb2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8cwwbYqI+w00egCRCaNukq5DD3eWu7cnLa6VwLpjfl8=; b=Z4KS2LpeICXBbufeEGrlLNWWlVWup0ltsImdS20b480xEUpV9yySUZ93LSkmpZWn0r fvJqK1AlwQ148S5HgNzpQltEhBaagySjXm30Ubg8NzvUKToWIvvqGqyklrDx5dg/V2rZ C/3nKUAy6L7WxVEUlILG71MdU/qv6ZlUaH3wan4TM0/cbV3aD7dnY33IzPr4kivJ8Uat u59i8NSlPTTdxKN2mRuJmkTkKG+v1IkfoxfQbHsZSC+BDhNkiLLmWQG8UzCcb1FTfipL dQ5Ye7482bmZ61zbHAKXkYVfvETp57amndWCSk63aqXJ7WFbf+sKIFqUQFwU8gLR8s7Z uMcQ== X-Gm-Message-State: AOAM532eMHtP3fk4Qy1FPXGgOf4vbzI1XoLGLLe2vdH9ZN9ovFaIq6wE aDKta5OBmbWfAoOrwhiEu1acrZ1ugX+T/IET5Ar/XA== X-Google-Smtp-Source: ABdhPJwuyB5h6povrFbiMjtqMOpCb6E8TBZ5NJvyyB9321D1vLDelW47KKU1IDrskoNZDpQoWnbS4JsCSuGMyJpMjdA= X-Received: by 2002:a05:622a:114:: with SMTP id u20mr9595291qtw.317.1616709543891; Thu, 25 Mar 2021 14:59:03 -0700 (PDT) MIME-Version: 1.0 References: <20210323035706.572953-1-joshdon@google.com> <20210324114224.GP15768@suse.de> <20210324133916.GQ15768@suse.de> <20210324155224.GR15768@suse.de> In-Reply-To: <20210324155224.GR15768@suse.de> From: Josh Don Date: Thu, 25 Mar 2021 14:58:52 -0700 Message-ID: Subject: Re: [PATCH v2] sched: Warn on long periods of pending need_resched To: Mel Gorman Cc: Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , Luis Chamberlain , Kees Cook , Iurii Zaikin , linux-kernel , linux-fsdevel@vger.kernel.org, David Rientjes , Oleg Rombakh , linux-doc@vger.kernel.org, Paul Turner Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Wed, Mar 24, 2021 at 01:39:16PM +0000, Mel Gorman wrote: > I'm not going to NAK because I do not have hard data that shows they must > exist. However, I won't ACK either because I bet a lot of tasty beverages > the next time we meet that the following parameters will generate reports > if removed. > > kernel.sched_latency_ns > kernel.sched_migration_cost_ns > kernel.sched_min_granularity_ns > kernel.sched_wakeup_granularity_ns > > I know they are altered by tuned for different profiles and some people do > go the effort to create custom profiles for specific applications. They > also show up in "Official Benchmarking" such as SPEC CPU 2017 and > some vendors put a *lot* of effort into SPEC CPU results for bragging > rights. They show up in technical books and best practice guids for > applications. Finally they show up in Google when searching for "tuning > sched_foo". I'm not saying that any of these are even accurate or a good > idea, just that they show up near the top of the results and they are > sufficiently popular that they might as well be an ABI. +1, these seem like sufficiently well-known scheduler tunables, and not really SCHED_DEBUG.