Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755164Ab3GJSdj (ORCPT ); Wed, 10 Jul 2013 14:33:39 -0400 Received: from emvm-gh1-uea09.nsa.gov ([63.239.67.10]:59381 "EHLO nsa.gov" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755083Ab3GJSdh (ORCPT ); Wed, 10 Jul 2013 14:33:37 -0400 X-TM-IMSS-Message-ID: <2948f8af000c2c44@nsa.gov> Message-ID: <51DDA8E0.4030001@tycho.nsa.gov> Date: Wed, 10 Jul 2013 14:33:04 -0400 From: Stephen Smalley Organization: National Security Agency User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Waiman Long CC: James Morris , Eric Paris , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, "Chandramouleeswaran, Aswin" , "Norton, Scott J" Subject: Re: [PATCH v2 2/2] SELinux: Increase ebitmap_node size for 64-bit configuration References: <1370466902-21144-1-git-send-email-Waiman.Long@hp.com> <1370466902-21144-2-git-send-email-Waiman.Long@hp.com> In-Reply-To: <1370466902-21144-2-git-send-email-Waiman.Long@hp.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1929 Lines: 50 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 Acked-by: Stephen Smalley > --- > 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 > > -#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) > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/