From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757689AbcDEI4M (ORCPT ); Tue, 5 Apr 2016 04:56:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59725 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757557AbcDEI4K (ORCPT ); Tue, 5 Apr 2016 04:56:10 -0400 Date: Tue, 5 Apr 2016 10:56:07 +0200 From: Jiri Olsa To: Peter Zijlstra Cc: Rik van Riel , Ingo Molnar , James Hartsock , Srivatsa Vaddagiri , Kirill Tkhai , linux-kernel@vger.kernel.org Subject: Re: [RFC] sched: unused cpu in affine workload Message-ID: <20160405085607.GE17232@krava.brq.redhat.com> References: <20160404082302.GB2137@krava.local> <20160404085944.GA3030@gmail.com> <20160404091951.GA10360@gmail.com> <20160404093844.GA16017@gmail.com> <20160404132321.GZ3448@twins.programming.kicks-ass.net> <1459799116.6219.24.camel@redhat.com> <20160404213450.GE3448@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160404213450.GE3448@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 04, 2016 at 11:34:50PM +0200, Peter Zijlstra wrote: > On Mon, Apr 04, 2016 at 03:45:16PM -0400, Rik van Riel wrote: > > An optimal solution is NP hard. > > > > Heuristics that "move tasks with pressure" may be > > much more doable, and lead to perfectly satisfactory > > results, especially if most migrations happen within > > a socket (and the same shared L3 cache). > > Right; trick will be finding something that mostly works without making > the regular balance paths increase in complexity. > > As per the argument in kernel/sched/fair.c:5694 the current > load-balancing averages out to O(n), and I would very much like to keep > it that way. guys, thanks a lot for all the thoughts and suggestions, I'll try to come up with something jirka