netdev - [NETFILTER] xt_hashlimit : speedups hash

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Date:	Fri, 14 Dec 2007 12:09:31 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: [NETFILTER] xt_hashlimit : speedups hash_dst()

1) Using jhash2() instead of jhash() is a litle bit faster if applicable.

2) Thanks to jhash, hash value uses full 32 bits.
    Instead of returning hash % size (implying a divide)
    we return the high 32 bits of the (hash * size) that will
    give results between [0 and size-1] and same hash distribution.

   On most cpus, a multiply is less expensive than a divide, by an order
   of magnitude.
  
Signed-off-by: Eric Dumazet <dada1@...mosbay.com>



View attachment "xt_hashlimit.patch" of type "text/plain" (856 bytes)