From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f47.google.com (mail-wg0-f47.google.com [74.125.82.47]) by kanga.kvack.org (Postfix) with ESMTP id 529A76B0031 for ; Wed, 19 Feb 2014 03:16:48 -0500 (EST) Received: by mail-wg0-f47.google.com with SMTP id k14so46504wgh.2 for ; Wed, 19 Feb 2014 00:16:47 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n6si17144794wjf.5.2014.02.19.00.16.46 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 19 Feb 2014 00:16:46 -0800 (PST) Date: Wed, 19 Feb 2014 09:16:44 +0100 From: Michal Hocko Subject: Re: ppc: RECLAIM_DISTANCE 10? Message-ID: <20140219081644.GA14783@dhcp22.suse.cz> References: <20140218090658.GA28130@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Anton Blanchard , Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, LKML On Tue 18-02-14 14:27:11, David Rientjes wrote: > On Tue, 18 Feb 2014, Michal Hocko wrote: > > > 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. > > > > I strongly suspect that the patch is correct since powerpc node distances > are different than the architectures you're talking about and get doubled > for every NUMA domain that the hardware supports. Even if the units of the distance is different on PPC should every NUMA machine have zone_reclaim enabled? That doesn't right to me. -- 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