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net: speedup udp receive path

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Since commit 95766fff ([UDP]: Add memory accounting.), 
each received packet needs one extra sock_lock()/sock_release() pair.

This added latency because of possible backlog handling. Then later,
ticket spinlocks added yet another latency source in case of DDOS.

This patch introduces lock_sock_bh() and unlock_sock_bh()
synchronization primitives, avoiding one atomic operation and backlog
processing.

skb_free_datagram_locked() uses them instead of full blown
lock_sock()/release_sock(). skb is orphaned inside locked section for
proper socket memory reclaim, and finally freed outside of it.

UDP receive path now take the socket spinlock only once.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2010-04-28 14:35:48 -07:00
committed by David S. Miller
parent cfc1fbb079
commit 4b0b72f7dd
4 changed files with 25 additions and 11 deletions
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10
include/net/sock.h
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@@ -1021,6 +1021,16 @@ extern void release_sock(struct sock *sk);
SINGLE_DEPTH_NESTING)
#define bh_unlock_sock(__sk) spin_unlock(&((__sk)->sk_lock.slock))
static inline void lock_sock_bh(struct sock *sk)
{
spin_lock_bh(&sk->sk_lock.slock);
}
static inline void unlock_sock_bh(struct sock *sk)
{
spin_unlock_bh(&sk->sk_lock.slock);
}
extern struct sock *sk_alloc(struct net *net, int family,
gfp_t priority,
struct proto *prot);