From: David Held <drheld@google.com>
Date: Wed, 16 Jul 2014 03:28:32 +0000 (-0400)
Subject: udp: Use hash2 for long hash1 chains in __udp*_lib_mcast_deliver.
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~149^2~144^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2dc41cff7545d55c6294525c811594576f8e119c;p=pandora-kernel.git

udp: Use hash2 for long hash1 chains in __udp*_lib_mcast_deliver.

Many multicast sources can have the same port which can result in a very
large list when hashing by port only. Hash by address and port instead
if this is the case. This makes multicast more similar to unicast.

On a 24-core machine receiving from 500 multicast sockets on the same
port, before this patch 80% of system CPU was used up by spin locking
and only ~25% of packets were successfully delivered.

With this patch, all packets are delivered and kernel overhead is ~8%
system CPU on spinlocks.

Signed-off-by: David Held <drheld@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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