From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f177.google.com (mail-wi0-f177.google.com [209.85.212.177]) by kanga.kvack.org (Postfix) with ESMTP id E0AC66B0035 for ; Tue, 18 Feb 2014 04:07:02 -0500 (EST) Received: by mail-wi0-f177.google.com with SMTP id e4so3228857wiv.4 for ; Tue, 18 Feb 2014 01:07:02 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id ez4si13719366wjd.25.2014.02.18.01.07.00 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 18 Feb 2014 01:07:01 -0800 (PST) Date: Tue, 18 Feb 2014 10:06:58 +0100 From: Michal Hocko 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 Sender: owner-linux-mm@kvack.org List-ID: To: Anton Blanchard Cc: Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, LKML 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org