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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 2679CC2D0E4 for ; Thu, 19 Nov 2020 14:17:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 47125238E6 for ; Thu, 19 Nov 2020 14:17:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 47125238E6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 62A676B006E; Thu, 19 Nov 2020 09:17:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5DAF16B0071; Thu, 19 Nov 2020 09:17:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4A4146B0073; Thu, 19 Nov 2020 09:17:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0140.hostedemail.com [216.40.44.140]) by kanga.kvack.org (Postfix) with ESMTP id 1EA956B006E for ; Thu, 19 Nov 2020 09:17:08 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B7B01181AEF1F for ; Thu, 19 Nov 2020 14:17:07 +0000 (UTC) X-FDA: 77501369694.02.fall95_0a172ae27343 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id 979DE10097AA1 for ; Thu, 19 Nov 2020 14:17:07 +0000 (UTC) X-HE-Tag: fall95_0a172ae27343 X-Filterd-Recvd-Size: 2553 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Thu, 19 Nov 2020 14:17:06 +0000 (UTC) Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E363E22210; Thu, 19 Nov 2020 14:17:03 +0000 (UTC) Date: Thu, 19 Nov 2020 09:17:02 -0500 From: Steven Rostedt To: Mel Gorman Cc: Peter Zijlstra , Thomas Gleixner , LKML , x86@kernel.org, Linus Torvalds , Christoph Hellwig , Matthew Wilcox , Daniel Vetter , Andrew Morton , linux-mm@kvack.org, Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Daniel Bristot de Oliveira , Linus Torvalds Subject: Re: [patch V4 4/8] sched: Make migrate_disable/enable() independent of RT Message-ID: <20201119091702.59aac061@gandalf.local.home> In-Reply-To: <20201119121413.GI3306@suse.de> References: <20201118194838.753436396@linutronix.de> <20201118204007.269943012@linutronix.de> <20201119093834.GH3306@suse.de> <20201119111411.GL3121378@hirez.programming.kicks-ass.net> <20201119121413.GI3306@suse.de> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 19 Nov 2020 12:14:13 +0000 Mel Gorman wrote: > * Usage of migrate_disable is heavily discouraged as it is extremely > * hazardous on PREEMPT_RT kernels and any usage needs to be heavily I don't believe it's just PREEMPT_RT. It's RT tasks that are concerned, especially when you are dealing with SCHED_DEADLINE. PREEMPT_RT just allows better determinism for RT tasks, but the issue with migrate_disable is not limited to just PREEMPT_RT. -- Steve > * justified. Before even thinking about using this, read > * "Migrate-Disable and why it is undesired" in > * include/linux/preempt.h and include both a comment and document > * in the changelog why the use case is an exception.