From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965222AbeBMPKm (ORCPT ); Tue, 13 Feb 2018 10:10:42 -0500 Received: from merlin.infradead.org ([205.233.59.134]:33716 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965054AbeBMPKl (ORCPT ); Tue, 13 Feb 2018 10:10:41 -0500 Date: Tue, 13 Feb 2018 16:10:33 +0100 From: Peter Zijlstra To: Mel Gorman Cc: Ingo Molnar , Mike Galbraith , Matt Fleming , Giovanni Gherdovich , LKML Subject: Re: [PATCH 6/6] sched/numa: Delay retrying placement for automatic NUMA balance after wake_affine Message-ID: <20180213151033.GP25201@hirez.programming.kicks-ass.net> References: <20180213133730.24064-1-mgorman@techsingularity.net> <20180213133730.24064-7-mgorman@techsingularity.net> <20180213140137.GN25201@hirez.programming.kicks-ass.net> <20180213141812.ikin7n2owi5uor3b@techsingularity.net> <20180213144326.GO25201@hirez.programming.kicks-ass.net> <20180213150020.xds3htkutdk4sdwx@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180213150020.xds3htkutdk4sdwx@techsingularity.net> 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 Tue, Feb 13, 2018 at 03:00:20PM +0000, Mel Gorman wrote: > On Tue, Feb 13, 2018 at 03:43:26PM +0100, Peter Zijlstra wrote: > > > > > > Well, it was deliberate. While it's possible to be on the same memory > > > node and not sharing cache, the scheduler typically is more concerned with > > > the LLC than NUMA per-se. If they share LLC, then I also assume that they > > > share memory locality. > > > > True, but the remaining code only has effect for numa balance, which is > > concerned with nodes. So I don't see the point of using something > > potentially smaller. > > > > Suppose someone did hardware where a node has 2 cache clusters, then > > we'd still set a wake_affine back-off for numa-balance, even though it > > remains on the same node. > > > > How would that be useful? > > Fair point, it could be unexpected from a NUMA balancing perspective and > sub-numa clustering does exist so it's a potential issue. I'm happy to > change it to cpu_to_node. I can resend the series if you prefer but feel > free to change it in-place if you're picking it up. I do not expect any > change on the machines I tested with as for all of them LLC was equivalent > to checking the node ID. OK, changed it locally. Thanks!