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udp: no longer use SLAB_DESTROY_BY_RCU

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Tom Herbert would like not touching UDP socket refcnt for encapsulated
traffic. For this to happen, we need to use normal RCU rules, with a grace
period before freeing a socket. UDP sockets are not short lived in the
high usage case, so the added cost of call_rcu() should not be a concern.

This actually removes a lot of complexity in UDP stack.

Multicast receives no longer need to hold a bucket spinlock.

Note that ip early demux still needs to take a reference on the socket.

Same remark for functions used by xt_socket and xt_PROXY netfilter modules,
but this might be changed later.

Performance for a single UDP socket receiving flood traffic from
many RX queues/cpus.

Simple udp_rx using simple recvfrom() loop :
438 kpps instead of 374 kpps : 17 % increase of the peak rate.

v2: Addressed Willem de Bruijn feedback in multicast handling
 - keep early demux break in __udp4_lib_demux_lookup()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <tom@herbertland.com>
Cc: Willem de Bruijn <willemb@google.com>
Tested-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-04-01 08:52:13 -07:00 • committed by David S. Miller
parent a4298e4522
commit ca065d0cf8
6 changed files with 172 additions and 359 deletions
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8
include/linux/udp.h
View file

@ -98,11 +98,11 @@ static inline bool udp_get_no_check6_rx(struct sock *sk)
return udp_sk(sk)->no_check6_rx;
}
#define udp_portaddr_for_each_entry(__sk, node, list) \
hlist_nulls_for_each_entry(__sk, node, list, __sk_common.skc_portaddr_node)
#define udp_portaddr_for_each_entry(__sk, list) \
hlist_for_each_entry(__sk, list, __sk_common.skc_portaddr_node)
#define udp_portaddr_for_each_entry_rcu(__sk, node, list) \
hlist_nulls_for_each_entry_rcu(__sk, node, list, __sk_common.skc_portaddr_node)
#define udp_portaddr_for_each_entry_rcu(__sk, list) \
hlist_for_each_entry_rcu(__sk, list, __sk_common.skc_portaddr_node)
#define IS_UDPLITE(__sk) (udp_sk(__sk)->pcflag)