From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751117AbeBIMhM (ORCPT ); Fri, 9 Feb 2018 07:37:12 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:52833 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750924AbeBIMhL (ORCPT ); Fri, 9 Feb 2018 07:37:11 -0500 Date: Fri, 9 Feb 2018 13:37:04 +0100 From: Peter Zijlstra To: Joel Fernandes Cc: Rohit Jain , Ingo Molnar , LKML , steven.sistare@oracle.com, dhaval.giani@oracle.com, Dietmar Eggemann , Vincent Guittot , Morten Rasmussen , "Cc: EAS Dev" Subject: Re: [RESEND PATCH] sched/fair: consider RT/IRQ pressure in select_idle_sibling Message-ID: <20180209123704.GN25201@hirez.programming.kicks-ass.net> References: <1517268429-933-1-git-send-email-rohit.k.jain@oracle.com> <6967b972-129a-a7f0-06ab-c48dc9709726@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 05, 2018 at 10:50:41PM -0800, Joel Fernandes wrote: > That's Ok with me. Just that I remember Peter messing with this path > and that it was expensive to scan too much for some systems. The other > thing is you're really doing to do a "fail safe" as you call it search > here with SIS_PROP set. Do you see a difference in perf when doing the > same approach as you took in select_idle_core? > > Peter, are you with the approach Rohit has adopted to pick best > capacity idle CPU in select_idle_cpu? I guess nr--; will bail out > early if we have SIS_PROP set, incase the scan cost gets too much but > then again we might end scanning too few CPUs. _IF_ you want to consider capacity, I don't think there's much else you can do. And yes, nr-- might have to save the day more often.