Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760305AbZCSWxN (ORCPT ); Thu, 19 Mar 2009 18:53:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756122AbZCSWw4 (ORCPT ); Thu, 19 Mar 2009 18:52:56 -0400 Received: from gir.skynet.ie ([193.1.99.77]:50865 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750933AbZCSWwz (ORCPT ); Thu, 19 Mar 2009 18:52:55 -0400 Date: Thu, 19 Mar 2009 22:52:52 +0000 From: Mel Gorman To: Christoph Lameter Cc: Linux Memory Management List , Pekka Enberg , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin , Linux Kernel Mailing List , Lin Ming , Zhang Yanmin , Peter Zijlstra Subject: Re: [PATCH 20/35] Use a pre-calculated value for num_online_nodes() Message-ID: <20090319225252.GF24586@csn.ul.ie> References: <20090318150833.GC4629@csn.ul.ie> <20090318180152.GB24462@csn.ul.ie> <20090319212912.GB24586@csn.ul.ie> <20090319223353.GE24586@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2049 Lines: 52 On Thu, Mar 19, 2009 at 06:42:39PM -0400, Christoph Lameter wrote: > On Thu, 19 Mar 2009, Mel Gorman wrote: > > > I posted an amalgamation. Sorry for the cross-over mails but I wanted to > > get tests going before I fell asleep. They take a few hours to complete. > > > > > > static inline void node_set_state(int node, enum node_states state) > > > > { > > > > __node_set(node, &node_states[state]); > > > > + if (state == N_ONLINE) > > > > + nr_online_nodes = num_node_state(N_ONLINE); > > > > } > > > > > > That assumes uses of node_set_state N_ONLINE. Are there such users or are > > > all using node_set_online()? > > > > > > > node_set_online() calls node_set_state(node, N_ONLINE) so it should have > > worked out. > > But this adds a surprising side effect to all uses of node_set_state. > Node_set_state is generating more code now. > Fair point. > > > if you want to check if the system could ever bring up a second node > > > (which would make the current optimization not viable) whereas > > > nr_online_nodes is the check for how many nodes are currently online. > > > > > > > I redid your patch to drop the nr_possible_nodes() because I couldn't convince > > myself it was correct in all cases and it isn't as important as avoiding > > num_online_nodes() in fast paths. > > I was more thinking about getting the infrastructure right so that we can > avoid future hacks like the one in slab. > Which is fair enough and you're right in that it's worth fixing. One horribly large patchset and associcate thread at a time though so I'll be putting it on the wrong finger rather than adding this to the pile right now :). -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/