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,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 DC780C433E2 for ; Wed, 24 Mar 2021 11:43:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B531961A12 for ; Wed, 24 Mar 2021 11:43:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233029AbhCXLml (ORCPT ); Wed, 24 Mar 2021 07:42:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:47320 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230489AbhCXLmc (ORCPT ); Wed, 24 Mar 2021 07:42:32 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5E505AD38; Wed, 24 Mar 2021 11:42:27 +0000 (UTC) Date: Wed, 24 Mar 2021 11:42:24 +0000 From: Mel Gorman To: Peter Zijlstra Cc: Josh Don , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , Luis Chamberlain , Kees Cook , Iurii Zaikin , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, David Rientjes , Oleg Rombakh , linux-doc@vger.kernel.org, Paul Turner Subject: Re: [PATCH v2] sched: Warn on long periods of pending need_resched Message-ID: <20210324114224.GP15768@suse.de> References: <20210323035706.572953-1-joshdon@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 24, 2021 at 11:54:24AM +0100, Peter Zijlstra wrote: > On Wed, Mar 24, 2021 at 10:37:43AM +0100, Peter Zijlstra wrote: > > Should we perhaps take out all SCHED_DEBUG sysctls and move them to > > /debug/sched/ ? (along with the existing /debug/sched_{debug,features,preemp} > > files) > > > > Having all that in sysctl and documented gives them far too much sheen > > of ABI. > > ... a little something like this ... > I did not read this particularly carefully or boot it to check but some of the sysctls moved are expected to exist and should never should have been under SCHED_DEBUG. For example, I'm surprised that numa_balancing is under the SCHED_DEBUG sysctl because there are legimiate reasons to disable that at runtime. For example, HPC clusters running various workloads may disable NUMA balancing globally for particular jobs without wanting to reboot and reenable it when finished. Moving something like sched_min_granularity_ns will break a number of tuning guides as well as the "tuned" tool which ships by default with some distros and I believe some of the default profiles used for tuned tweak kernel.sched_min_granularity_ns Whether there are legimiate reasons to modify those values or not, removing them may generate fun bug reports. -- Mel Gorman SUSE Labs