From mboxrd@z Thu Jan 1 00:00:00 1970 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: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Steve Bergman Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org