linux-kernel - Re: [PATCH] slab: implement kmalloc guard

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Message-ID: <alpine.DEB.2.11.1409081108190.20388@gentwo.org>
Date:	Mon, 8 Sep 2014 11:10:22 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Mikulas Patocka <mpatocka@...hat.com>
cc:	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	"Alasdair G. Kergon" <agk@...hat.com>,
	Mike Snitzer <msnitzer@...hat.com>,
	Milan Broz <gmazyland@...il.com>, kkolasa@...soft.pl,
	dm-devel@...hat.com
Subject: Re: [PATCH] slab: implement kmalloc guard

On Mon, 8 Sep 2014, Mikulas Patocka wrote:

> I don't know what you mean. If someone allocates 10000 objects with sizes
> from 1 to 10000, you can't have 10000 slab caches - you can't have a slab
> cache for each used size. Also - you can't create a slab cache in
> interrupt context.

Oh you can create them up front on bootup. And I think only the small
sizes matter. Allocations >=8K are pushed to the page allocator anyways.

> > We already have a redzone structure to check for writes over the end of
> > the object. Lets use that.
>
> So, change all three slab subsystems to use that.

SLOB has no debugging features and I think that was intentional. We are
trying to unify the debug checks etc. Some work on that would be
appreciated. I think the kmalloc creation is already in slab_common.c

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