linux-kernel - Re: [PATCH v2 2/2] SELinux: Increase ebitmap

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Date:	Wed, 10 Jul 2013 15:59:29 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	Waiman Long <Waiman.Long@...com>,
	Eric Paris <eparis@...isplace.org>
Cc:	Stephen Smalley <sds@...ho.nsa.gov>,
	James Morris <james.l.morris@...cle.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>, selinux@...ho.nsa.gov
Subject: Re: [PATCH v2 2/2] SELinux: Increase ebitmap_node size for 64-bit configuration

On Wednesday, July 10, 2013 02:33:04 PM Stephen Smalley wrote:
> On 06/05/2013 05:15 PM, Waiman Long wrote:
> > Currently, the ebitmap_node structure has a fixed size of 32 bytes. On
> > a 32-bit system, the overhead is 8 bytes, leaving 24 bytes for being
> > used as bitmaps. The overhead ratio is 1/4.
> > 
> > On a 64-bit system, the overhead is 16 bytes. Therefore, only 16 bytes
> > are left for bitmap purpose and the overhead ratio is 1/2. With a
> > 3.8.2 kernel, a boot-up operation will cause the ebitmap_get_bit()
> > function to be called about 9 million times. The average number of
> > ebitmap_node traversal is about 3.7.
> > 
> > This patch increases the size of the ebitmap_node structure to 64
> > bytes for 64-bit system to keep the overhead ratio at 1/4. This may
> > also improve performance a little bit by making node to node traversal
> > less frequent (< 2) as more bits are available in each node.
> > 
> > Signed-off-by: Waiman Long <Waiman.Long@...com>
> 
> Acked-by:  Stephen Smalley <sds@...ho.nsa.gov>

Looks good to me too.  Merged, built, and tested okay too.

 * git://git.infradead.org/users/pcmoore/lblnet-2.6_next

> > ---
> > 
> >   security/selinux/ss/ebitmap.h |    8 +++++++-
> >   1 files changed, 7 insertions(+), 1 deletions(-)
> > 
> > diff --git a/security/selinux/ss/ebitmap.h b/security/selinux/ss/ebitmap.h
> > index e7eb3a9..712c8a7 100644
> > --- a/security/selinux/ss/ebitmap.h
> > +++ b/security/selinux/ss/ebitmap.h
> > @@ -16,7 +16,13 @@
> > 
> >   #include <net/netlabel.h>
> > 
> > -#define EBITMAP_UNIT_NUMS	((32 - sizeof(void *) - sizeof(u32))	\
> > +#ifdef CONFIG_64BIT
> > +#define	EBITMAP_NODE_SIZE	64
> > +#else
> > +#define	EBITMAP_NODE_SIZE	32
> > +#endif
> > +
> > +#define EBITMAP_UNIT_NUMS	((EBITMAP_NODE_SIZE-sizeof(void
> > *)-sizeof(u32))\
> > 
> >   					/ sizeof(unsigned long))
> >   
> >   #define EBITMAP_UNIT_SIZE	BITS_PER_LONG
> >   #define EBITMAP_SIZE		(EBITMAP_UNIT_NUMS * EBITMAP_UNIT_SIZE)
> 
> --
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-- 
paul moore
www.paul-moore.com

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