linux-kernel - Re: min_free_kbytes documentation, /proc/sys/vm docs

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Message-Id: <1187013180.20108.59.camel@twins>
Date:	Mon, 13 Aug 2007 15:53:00 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Pavel Machek <pavel@....cz>
Cc:	Andrew Morton <akpm@...l.org>,
	kernel list <linux-kernel@...r.kernel.org>, andrea@...e.de,
	npiggin@...e.de
Subject: Re: min_free_kbytes documentation, /proc/sys/vm docs

On Mon, 2007-08-13 at 15:46 +0200, Pavel Machek wrote:
> Hi!
> 
> min_free_kbytes documentation says:
> 
> min_free_kbytes:
> 
> This is used to force the Linux VM to keep a minimum number 
> of kilobytes free.  The VM uses this number to compute a pages_min
> value for each lowmem zone in the system.  Each lowmem zone gets 
> a number of reserved free pages based proportionally on its size.
> 
> ....which is not too helpful :-(. In particular, should kernel survive
> setting this to 0 and still work reliably? IOW is this
> performance-only tweak, or does it correctness implications?

correctness

sort-of, since PF_MEMALLOC usage is currently un-bounded.

> I guess it should also say something like "do not set this to more
> than half of your physical RAM (or half of lowmem?) or you get an
> instant OOM".

yeah, lowmem, not sure on the oom part, it should work with quite high
limits, although I've never tried it with ridiculous numbers.

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