From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751248AbdE3M2k (ORCPT ); Tue, 30 May 2017 08:28:40 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:60208 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750898AbdE3M2j (ORCPT ); Tue, 30 May 2017 08:28:39 -0400 Date: Tue, 30 May 2017 14:28:31 +0200 From: Peter Zijlstra To: Rohit Jain Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, vincent.guittot@linaro.org, morten.rasmussen@arm.com, dietmar.eggemann@arm.com Subject: Re: [PATCH] sched: Introduce scaled capacity awareness in enqueue Message-ID: <20170530122831.5fyywtplq4jawj3j@hirez.programming.kicks-ass.net> References: <1495486094-9097-1-git-send-email-rohit.k.jain@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1495486094-9097-1-git-send-email-rohit.k.jain@oracle.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 22, 2017 at 01:48:14PM -0700, Rohit Jain wrote: > The patch introduces capacity awarness in scheduler (CAS) which avoids > CPUs which might have their capacities reduced (due to IRQ/RT activity) > when trying to schedule threads (on the push side) in the system. This > awareness has been added into the fair scheduling class. > > It does so by, using the following algorithm: > -------------------------------------------------------------------------- > 1) As in rt_avg the scaled capacities are already calculated. > > 2) This scaled capacity is normalized and mapped into buckets. Why? > 3) Any CPU which lies below the 80th percentile in terms of percentage > capacity available is considered as a low capacity CPU. Random number; can we do better? What does existing code do?