linux-kernel - Re: [PATCH 5/6] selinux: improve role transition hashing

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Message-ID: <48756a04aea9d076c3a35ff4c9257dce.paul@paul-moore.com>
Date:   Wed, 13 Sep 2023 13:46:55 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Christian Göttsche <cgzones@...glemail.com>,
        selinux@...r.kernel.org
Cc:     Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] selinux: improve role transition hashing

On Aug 18, 2023 =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@...glemail.com> wrote:
> 
> The number of buckets is calculated by performing a binary AND against
> the mask of the hash table, which is one less than its size (which is a
> power of two).  This leads to all top bits being discarded, e.g. with
> the Reference Policy on Debian there exists 376 entries, leading to a
> size of 512, discarding the top 23 bits.
> 
> Use jhash to improve the hash table utilization:
> 
>     # current
>     roletr:  376 entries and 124/512 buckets used, longest chain length 8, sum of chain length^2 1496
> 
>     # patch
>     roletr:  376 entries and 266/512 buckets used, longest chain length 4, sum of chain length^2 646
> 
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
> Reviewed-by: Stephen Smalley <stephen.smalley.work@...il.com>
> ---
>  security/selinux/ss/policydb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Merged into selinux/next, thanks.

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