From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750870AbWERHVx (ORCPT ); Thu, 18 May 2006 03:21:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750858AbWERHVx (ORCPT ); Thu, 18 May 2006 03:21:53 -0400 Received: from mail25.syd.optusnet.com.au ([211.29.133.166]:228 "EHLO mail25.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S1750839AbWERHVw (ORCPT ); Thu, 18 May 2006 03:21:52 -0400 From: Con Kolivas To: Nick Piggin Subject: Re: [PATCH] mm: limit lowmem_reserve Date: Thu, 18 May 2006 17:21:38 +1000 User-Agent: KMail/1.9.1 Cc: Andrew Morton , ck@vds.kolivas.org, linux list , linux-mm@kvack.org References: <200604021401.13331.kernel@kolivas.org> <200605180011.43216.kernel@kolivas.org> <446C1E25.4080408@yahoo.com.au> In-Reply-To: <446C1E25.4080408@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200605181721.38735.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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. -- -ck