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Date: 05 Oct 2006 22:01:53 +0200 From: Andi Kleen <ak@...e.de> To: Steve Bergman <sbergman@...b.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: Free memory level in 2.6.16? Steve Bergman <sbergman@...b.com> 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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