From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755739Ab0JLGlR (ORCPT ); Tue, 12 Oct 2010 02:41:17 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:51704 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753641Ab0JLGlQ (ORCPT ); Tue, 12 Oct 2010 02:41:16 -0400 Date: Tue, 12 Oct 2010 12:11:08 +0530 From: Balbir Singh To: KOSAKI Motohiro Cc: David Rientjes , Christoph Lameter , Mel Gorman , Rob Mueller , linux-kernel@vger.kernel.org, Bron Gondwana , linux-mm Subject: Re: [resend][PATCH] mm: increase RECLAIM_DISTANCE to 30 Message-ID: <20101012064108.GE25875@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20101012111451.AD2E.A69D9226@jp.fujitsu.com> <20101012130806.AD37.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20101012130806.AD37.A69D9226@jp.fujitsu.com> 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 * KOSAKI Motohiro [2010-10-12 13:07:35]: > > On Tue, 12 Oct 2010, KOSAKI Motohiro wrote: > > > > > > It doesn't determine what the maximum latency to that memory is, it relies > > > > on whatever was defined in the SLIT; the only semantics of that distance > > > > comes from the ACPI spec that states those distances are relative to the > > > > local distance of 10. > > > > > > Right. but do we need to consider fake SLIT case? I know actually such bogus > > > slit are there. but I haven't seen such fake SLIT made serious trouble. > > > > > > > If we can make the assumption that the SLIT entries are truly > > representative of the latencies and are adhering to the semantics > > presented in the ACPI spec, then this means the VM prefers to do zone > > reclaim rather than from other nodes when the latter is 3x more costly. > > > > That's fine by me, as I've mentioned we've done this for a couple years > > because we've had to explicitly disable zone_reclaim_mode for such > > configurations. If that's the policy decision that's been made, though, > > we _could_ measure the cost at boot and set zone_reclaim_mode depending on > > the measured latency rather than relying on the SLIT at all in this case. > > ok, got it. thanks. > Could we please document the change and help people understand why with newer kernels they may see the value of zone_reclaim_mode change on their systems and how to set it back if required. -- Three Cheers, Balbir