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

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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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David Held 2014-07-15 23:28:32 -04:00 • committed by David S. Miller

parent 5cf3d46192

commit 2dc41cff75

3 changed files with 55 additions and 20 deletions

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14

include/net/sock.h

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31

net/ipv4/udp.c

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30

net/ipv6/udp.c

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