From: Eric Dumazet <edumazet@google.com>
Date: Fri, 7 Jun 2013 15:48:57 +0000 (-0700)
Subject: igmp: hash a hash table to speedup ip_check_mc_rcu()
X-Git-Tag: v3.11-rc1~16^2~121
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e9897071350bd9d94a56b5b6f79c85b1a98fc7e7;p=pandora-kernel.git

igmp: hash a hash table to speedup ip_check_mc_rcu()

After IP route cache removal, multicast applications using
a lot of multicast addresses hit a O(N) behavior in ip_check_mc_rcu()

Add a per in_device hash table to get faster lookup.

This hash table is created only if the number of items in mc_list is
above 4.

Reported-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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