From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964970AbWDDCfE (ORCPT ); Mon, 3 Apr 2006 22:35:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964973AbWDDCfD (ORCPT ); Mon, 3 Apr 2006 22:35:03 -0400 Received: from mail13.syd.optusnet.com.au ([211.29.132.194]:30673 "EHLO mail13.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S964970AbWDDCfB (ORCPT ); Mon, 3 Apr 2006 22:35:01 -0400 From: Con Kolivas To: ck@vds.kolivas.org Subject: Re: [ck] lowmem_reserve question Date: Tue, 4 Apr 2006 12:35:59 +1000 User-Agent: KMail/1.8.3 Cc: Nick Piggin , Andrew Morton , linux list References: <200604021401.13331.kernel@kolivas.org> <442F9E91.1020306@yahoo.com.au> <200604031248.13532.kernel@kolivas.org> In-Reply-To: <200604031248.13532.kernel@kolivas.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200604041235.59876.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 3 Apr 2006 12:48 pm, Con Kolivas wrote: > While trying to digest just what the lowmem_reserve does > and how it's utilised I looked at some of the numbers > > int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = { 256, 256, 32 }; > > lower_zone->lowmem_reserve[j] = present_pages / > sysctl_lowmem_reserve_ratio[idx]; > > This is interesting because there are no bounds on this value and it seems > possible to set the sysctl to have a lowmem_reserve that is larger than the > zone size. Ok that's a sysctl so if a user is setting it wrongly that's > their fault... or should there be some upper bound? > > Furthermore, now that we have the option of up to 3GB lowmem split on 32bit > we can have a default lowmem_reserve of almost 12MB (if I'm reading it > right) which seems very tight with only 16MB of ZONE_DMA. > > On a basically idle 1GB lowmem box that I have it looks like this: > > Node 0, zone DMA > pages free 1025 > min 15 > low 18 > high 22 > active 2185 > inactive 0 > scanned 555 (a: 21 i: 6) > spanned 4096 > present 4096 > protection: (0, 0, 1007, 1007) > > With 3GB lowmem the default settings seem too tight to me. The way I see > it, there should be some upper bounds on the lowmem reserves. Or perhaps > I'm just missing something again... I'm feeling even thicker than usual. Silence. Low priority I guess. If I propose a patch that might get some response. /me threatens to post a patch. Cheers, Con