From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755390AbaEFUVe (ORCPT ); Tue, 6 May 2014 16:21:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47364 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754028AbaEFUVb (ORCPT ); Tue, 6 May 2014 16:21:31 -0400 Message-ID: <5369442B.9010505@redhat.com> Date: Tue, 06 May 2014 16:20:59 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Preeti Murthy , umgwanakikbuti@gmail.com, LKML , Morten Rasmussen , Ingo Molnar , george.mccollister@gmail.com, ktkhai@parallels.com, Preeti U Murthy Subject: Re: [PATCH RFC/TEST] sched: make sync affine wakeups work References: <20140502004237.79dd3de6@annuminas.surriel.com> <1399011219.5233.55.camel@marge.simpson.net> <53633B81.1080403@redhat.com> <53663565.9080306@redhat.com> <20140506132516.GJ11096@twins.programming.kicks-ass.net> In-Reply-To: <20140506132516.GJ11096@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/06/2014 09:25 AM, Peter Zijlstra wrote: > On Sun, May 04, 2014 at 08:41:09AM -0400, Rik van Riel wrote: >> Even on 8-node DL980 systems, the NUMA distance in the >> SLIT table is less than RECLAIM_DISTANCE, and we will >> do wake_affine across the entire system. > > Yeah, so the problem is that (AFAIK) ACPI doesn't actually specify a > metric for the SLIT distance. This (in as far as BIOS people would care > to stick to specs anyhow) has lead to the 'fun' situation where BIOS > engineers tweak SLIT table values to make OSes behave as they thing it > should. > > So if the BIOS engineer finds that this system should have < > RECLAIM_DISTANCE it will simply make the table such that the max SLIT > value is below that. > > And yes, I've seen this :-( It appears to be the case on the vast majority of the NUMA systems that are actually in use. To me, this suggests that we should probably deal with it. -- All rights reversed