From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753835AbaJNGrk (ORCPT ); Tue, 14 Oct 2014 02:47:40 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:43295 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751194AbaJNGrj (ORCPT ); Tue, 14 Oct 2014 02:47:39 -0400 Date: Tue, 14 Oct 2014 08:47:20 +0200 From: Peter Zijlstra To: Rik van Riel Cc: linux-kernel@vger.kernel.org, mgorman@suse.de, chegu_vinod@hp.com, mingo@kernel.org, efault@gmx.de, vincent.guittot@linaro.org Subject: Re: [PATCH RFC 1/5] sched,numa: build table of node hop distance Message-ID: <20141014064720.GA11483@worktop> References: <1412797050-8903-1-git-send-email-riel@redhat.com> <1412797050-8903-2-git-send-email-riel@redhat.com> <20141012131714.GE3015@worktop> <543A81E4.4090504@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <543A81E4.4090504@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 12, 2014 at 09:28:04AM -0400, Rik van Riel wrote: > On 10/12/2014 09:17 AM, Peter Zijlstra wrote: > >On Wed, Oct 08, 2014 at 03:37:26PM -0400, riel@redhat.com wrote: > >>+ sched_domains_numa_hops = kzalloc(sizeof(int) * nr_node_ids * nr_node_ids, GFP_KERNEL); > >>+ if (!sched_domains_numa_hops) > >>+ return; > > > >That's potentially a _BIG_ table (1M for a 512 node system). > >The node_distance has magic allocations and is of u8 size, is there any > >way we can re-use node_distance and avoid a second O(n^2) allocation? > > You are right, this should be a u8 at the least. > > Beyond that, I am not convinced that merging things into > the same array is worthwhile, since (IIRC) nr_node_ids > should be set to the actual number of nodes on the system > by then. The thing is, it looks like all you do is compare hop distance, and the order of the hop distances is the exact same order as the regular numa distance. I could not find a place where you use the actual hop value. So if all you're interested in is the relative ordering, that should be the same for both.