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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 9C721C432C0 for ; Mon, 25 Nov 2019 21:38:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B273207FD for ; Mon, 25 Nov 2019 21:38:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726926AbfKYVgx (ORCPT ); Mon, 25 Nov 2019 16:36:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:58770 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725945AbfKYVgx (ORCPT ); Mon, 25 Nov 2019 16:36:53 -0500 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 0534D20706; Mon, 25 Nov 2019 21:36:51 +0000 (UTC) Date: Mon, 25 Nov 2019 16:36:50 -0500 From: Steven Rostedt To: Qais Yousef Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched: rt: Make RT capacity aware Message-ID: <20191125163650.6a624fee@gandalf.local.home> In-Reply-To: <20191009104611.15363-1-qais.yousef@arm.com> References: <20191009104611.15363-1-qais.yousef@arm.com> 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry for the very late response... On Wed, 9 Oct 2019 11:46:11 +0100 Qais Yousef wrote: > ATM the uclamp value are only used for frequency selection; but on > heterogeneous systems this is not enough and we need to ensure that the > capacity of the CPU is >= uclamp_min. Which is what implemented here. Is it possible that the capacity can be fixed, where the process can just have a cpu mask of CPUs that has the capacity for it? Not that this will affect this patch now, but just something for the future. > > capacity_orig_of(cpu) >= rt_task.uclamp_min > > Note that by default uclamp.min is 1024, which means that RT tasks will > always be biased towards the big CPUs, which make for a better more > predictable behavior for the default case. > > Must stress that the bias acts as a hint rather than a definite > placement strategy. For example, if all big cores are busy executing > other RT tasks we can't guarantee that a new RT task will be placed > there. > > On non-heterogeneous systems the original behavior of RT should be > retained. Similarly if uclamp is not selected in the config. > > Signed-off-by: Qais Yousef Reviewed-by: Steven Rostedt (VMware) -- Steve