Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754739AbaBRJHH (ORCPT ); Tue, 18 Feb 2014 04:07:07 -0500 Received: from cantor2.suse.de ([195.135.220.15]:56703 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754580AbaBRJHB (ORCPT ); Tue, 18 Feb 2014 04:07:01 -0500 Date: Tue, 18 Feb 2014 10:06:58 +0100 From: Michal Hocko To: Anton Blanchard Cc: Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, LKML Subject: ppc: RECLAIM_DISTANCE 10? Message-ID: <20140218090658.GA28130@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I have just noticed that ppc has RECLAIM_DISTANCE reduced to 10 set by 56608209d34b (powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim). The commit message suggests that the zone reclaim is desirable for all NUMA configurations. History has shown that the zone reclaim is more often harmful than helpful and leads to performance problems. The default RECLAIM_DISTANCE for generic case has been increased from 20 to 30 around 3.0 (32e45ff43eaf mm: increase RECLAIM_DISTANCE to 30). I strongly suspect that the patch is incorrect and it should be reverted. Before I will send a revert I would like to understand what led to the patch in the first place. I do not see why would PPC use only LOCAL_DISTANCE and REMOTE_DISTANCE distances and in fact machines I have seen use different values. Anton, could you comment please? -- Michal Hocko SUSE Labs -- 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/