From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751136AbWJEUCE (ORCPT ); Thu, 5 Oct 2006 16:02:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751145AbWJEUCE (ORCPT ); Thu, 5 Oct 2006 16:02:04 -0400 Received: from mx1.suse.de ([195.135.220.2]:26000 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1751136AbWJEUCB (ORCPT ); Thu, 5 Oct 2006 16:02:01 -0400 To: Steve Bergman Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: Free memory level in 2.6.16? References: <1160034527.23009.7.camel@localhost> From: Andi Kleen Date: 05 Oct 2006 22:01:53 +0200 In-Reply-To: <1160034527.23009.7.camel@localhost> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Steve Bergman writes: > Due to some problems I was having with the CentOS4.4 kernel, I just > moved a box (x86 with 4GB ram) to 2.6.16.29 from kernel.org. > > All is well, but I am curious about one thing. This is a fairly memory > hungry box, serving about 40 gnome desktops via xdmcp. All VM settings > are at the default. Swappiness=60, min_free_kbytes=3831. > > However, it seems to seek out about 150MB for the level of free memory > that it maintains. Typically I see somewhere between 100MB an 500MB in > swap, buffers+cache is about 500MB, and 150MB is free. > > If I cat from /dev/md0 to /dev/null, the free memory does go down, to > 25MB or so, but then I can watch as it seeks out about 150MB of free > memory. > > To me, free memory is wasted memory. Is this a bug or a feature? Normally it keeps some memory free for interrupt handlers which cannot free other memory. But 150MB is indeed a lot, especially it's only in the ~900MB lowmem zone. You could play with /proc/sys/vm/lowmem_reserve_ratio but must likely some defaults need tweaking. -Andi