linux-kernel - Re: [PATCH 2/2] SLUB: Disable debugging if it increases the minimum page order

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Date:	Thu, 11 Jun 2009 11:49:19 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	linux-kernel@...r.kernel.org, mel@....ul.ie,
	Larry.Finger@...inger.net
Subject: Re: [PATCH 2/2] SLUB: Disable debugging if it increases the minimum
 page order

On Thu, 11 Jun 2009, Pekka Enberg wrote:

> My main point is that a lot of _testers_ will probably enable all SLUB
> debugging by default because we encourage them to and it's pretty bad
> that we end up causing order 1 allocations and oom conditions.

Other test methods (like PAGE_ALLOC debugging) also have significant side
effects.

> So I still think we need to fix _at minimum_ the kmalloc-4096 case
> (assuming Larry won't hit the same problem still). I see you're not
> happy with my patch so any suggestions how to handle that?

Add a warning to Kconfig that the higher order page allocations may
increase with debugging on for caches with object sizes near or equal to
PAGE_SIZE?

Its good to run with full debugging on for even the 4k sized caches.
Otherwise we wont be catching overruns there. But the debugging can cause
some side effects.

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