From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750735AbWERH0N (ORCPT ); Thu, 18 May 2006 03:26:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750858AbWERH0N (ORCPT ); Thu, 18 May 2006 03:26:13 -0400 Received: from smtp109.mail.mud.yahoo.com ([209.191.85.219]:40855 "HELO smtp109.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1750735AbWERH0M (ORCPT ); Thu, 18 May 2006 03:26:12 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=aAJlokpW6E+Zk9P0WUpWXbV9Lnq75eUc6ImQo7KTKxOGIEtxJZpjQQjieDtRyIIpsO3E3pphSY+FE2roRIo2i48Ktyw96giEeVZUvWjbrpqxhqsx0vNQtVPdi7URy9JvWmIl8ARHJ5OXbTJ/hyVAhxB1uyPwkIj1W+XS7Rq4Alk= ; Message-ID: <446C2191.70300@yahoo.com.au> Date: Thu, 18 May 2006 17:26:09 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Con Kolivas CC: Andrew Morton , ck@vds.kolivas.org, linux list , linux-mm@kvack.org Subject: Re: [PATCH] mm: limit lowmem_reserve References: <200604021401.13331.kernel@kolivas.org> <200605180011.43216.kernel@kolivas.org> <446C1E25.4080408@yahoo.com.au> <200605181721.38735.kernel@kolivas.org> In-Reply-To: <200605181721.38735.kernel@kolivas.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Con Kolivas wrote: > On Thursday 18 May 2006 17:11, Nick Piggin wrote: > >>If we're under memory pressure, kswapd will try to free up any candidate >>zone, yes. >> >> >>>On my test case this indeed happens and my ZONE_DMA never goes below 3000 >>>pages free. If I lower the reserve even further my pages free gets stuck >>>at 3208 and can't free any more, and doesn't ever drop below that either. >>> >>>Here is the patch I was proposing >> >>What problem does that fix though? > > > It's a generic concern and I honestly don't know how significant it is which > is why I'm asking if it needs attention. That concern being that any time > we're under any sort of memory pressure, ZONE_DMA will undergo intense > reclaim even though there may not really be anything specifically going on in > ZONE_DMA. It just seems a waste of cycles doing that. > If it doesn't have any/much pagecache or slab cache in it, there won't be intense reclaim; if it does then it can be reclaimed and the memory used. reclaim / allocation could be slightly smarter about scaling watermarks, however I don't think it is much of an issue at the moment. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com