Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761810AbZCSXzJ (ORCPT ); Thu, 19 Mar 2009 19:55:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756511AbZCSXyz (ORCPT ); Thu, 19 Mar 2009 19:54:55 -0400 Received: from smtp.ultrahosting.com ([74.213.174.254]:46208 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754375AbZCSXyy (ORCPT ); Thu, 19 Mar 2009 19:54:54 -0400 Date: Thu, 19 Mar 2009 18:42:39 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@qirst.com To: Mel Gorman 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() In-Reply-To: <20090319223353.GE24586@csn.ul.ie> Message-ID: References: <20090316163626.GJ24293@csn.ul.ie> <20090318150833.GC4629@csn.ul.ie> <20090318180152.GB24462@csn.ul.ie> <20090319212912.GB24586@csn.ul.ie> <20090319223353.GE24586@csn.ul.ie> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1516 Lines: 39 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. > > 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. -- 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/