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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A7FEC433EF for ; Sat, 9 Apr 2022 17:28:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242869AbiDIRas (ORCPT ); Sat, 9 Apr 2022 13:30:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231684AbiDIRan (ORCPT ); Sat, 9 Apr 2022 13:30:43 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0651E83036 for ; Sat, 9 Apr 2022 10:28:34 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 00A7C60DE3 for ; Sat, 9 Apr 2022 17:28:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B653CC385A4; Sat, 9 Apr 2022 17:28:30 +0000 (UTC) Date: Sat, 9 Apr 2022 13:28:29 -0400 From: Steven Rostedt To: Qais Yousef Cc: Vincent Guittot , Dietmar Eggemann , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, linux-kernel@vger.kernel.org, parth@linux.ibm.com, chris.hyser@oracle.com, pkondeti@codeaurora.org, Valentin.Schneider@arm.com, patrick.bellasi@matbug.net, David.Laight@aculab.com, pjt@google.com, pavel@ucw.cz, tj@kernel.org, qperret@google.com, tim.c.chen@linux.intel.com, Wei Wang Subject: Re: [PATCH 0/6] Add latency_nice priority Message-ID: <20220409132829.16b03d69@rorschach.local.home> In-Reply-To: <20220409170841.upcimeak2ch3aj35@wubuntu> References: <20220311161406.23497-1-vincent.guittot@linaro.org> <7a7e1e21-df3d-4623-d9cd-51f5272919d5@arm.com> <20220401121525.flngciwjtkn3mwlv@airbuntu> <20220409170841.upcimeak2ch3aj35@wubuntu> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 9 Apr 2022 18:08:41 +0100 Qais Yousef wrote: > One other corner case to consider if you're working on next version is what > should happen when there are multiple tasks of the same priority on the rq. RT > scheduler will push/pull tasks to ensure the task will get to run ASAP if > there's another cpu at lower priority is available. Seems a lot of complexity > to add to CFS, but at the same time if 2 important tasks require low latency > are on the same rq, one of them will suffer without introducing the ability to > migrate one of them where it can get to run sooner. Instead of having the greedy algorithm of the RT push/pull logic, how hard would it be to have the load balancer know of these tasks, and try to keep them on different CPUs? When two are queued on the same CPU, could it be possible to just trigger load balancing and let it do the work? -- Steve