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

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Message-ID: <alpine.DEB.1.10.0906111422360.11973@gentwo.org>
Date:	Thu, 11 Jun 2009 14:26:02 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org, Larry.Finger@...inger.net
Subject: Re: [PATCH 2/2] SLUB: Disable debugging if it increases the minimum
 page order

On Thu, 11 Jun 2009, Mel Gorman wrote:

> "With SLUB_DEBUG, enable debug on all caches unless the increased meta-data
> would force the minimum order up on order due to object sizes being near or
> equal the PAGE_SIZE. If SLUB_DEBUG must be enabled, specify slub_debug=A for
> 'All caches enable debug regardless'"

Hmmm... No SLUB_DEBUG just compiles the code in for debugging. Does not
enable anything.

But we could make SLUB_DEBUG_ON enable debugging except on those slabs
where the order increases (for which it does a printk saying that the
debugging was disabled) and then have a slub_debug=A option that
overrides the order check. Generally if you know that you have memory
corruption you would want to boot with slub_debug=A. If you just want
continuous checks then SLUB_DEBUG_ON would do the trick.

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