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Commit fa438ccf authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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[NET]: Keep sk_backlog near sk_lock 



sk_backlog is a critical field of struct sock. (known famous words)

It is (ab)used in hot paths, in particular in release_sock(), tcp_recvmsg(),
tcp_v4_rcv(), sk_receive_skb().

It really makes sense to place it next to sk_lock, because sk_backlog is only
used after sk_lock locked (and thus memory cache line in L1 cache). This
should reduce cache misses and sk_lock acquisition time.

(In theory, we could only move the head pointer near sk_lock, and leaving tail
far away, because 'tail' is normally not so hot, but keep it simple :) )

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e317f6f6

include/net/sock.h

+9 −9
Original line number Diff line number Diff line
@@ -202,6 +202,15 @@ struct sock { 
	unsigned short		sk_type;

	int			sk_rcvbuf;

	socket_lock_t		sk_lock;

	/*

	 * The backlog queue is special, it is always used with

	 * the per-socket spinlock held and requires low latency

	 * access. Therefore we special case it's implementation.

	 */

	struct {

		struct sk_buff *head;

		struct sk_buff *tail;

	} sk_backlog;

	wait_queue_head_t	*sk_sleep;

	struct dst_entry	*sk_dst_cache;

	struct xfrm_policy	*sk_policy[2];
@@ -221,15 +230,6 @@ struct sock { 
	int			sk_rcvlowat;

	unsigned long 		sk_flags;

	unsigned long	        sk_lingertime;

	/*

	 * The backlog queue is special, it is always used with

	 * the per-socket spinlock held and requires low latency

	 * access. Therefore we special case it's implementation.

	 */

	struct {

		struct sk_buff *head;

		struct sk_buff *tail;

	} sk_backlog;

	struct sk_buff_head	sk_error_queue;

	struct proto		*sk_prot_creator;

	rwlock_t		sk_callback_lock;

net/core/sock.c

+1 −1
Original line number Diff line number Diff line
@@ -904,6 +904,7 @@ struct sock *sk_clone(const struct sock *sk, const gfp_t priority) 
		sk_node_init(&newsk->sk_node);

		sock_lock_init(newsk);

		bh_lock_sock(newsk);

		newsk->sk_backlog.head	= newsk->sk_backlog.tail = NULL;



		atomic_set(&newsk->sk_rmem_alloc, 0);

		atomic_set(&newsk->sk_wmem_alloc, 0);
@@ -923,7 +924,6 @@ struct sock *sk_clone(const struct sock *sk, const gfp_t priority) 
		newsk->sk_wmem_queued	= 0;

		newsk->sk_forward_alloc = 0;

		newsk->sk_send_head	= NULL;

		newsk->sk_backlog.head	= newsk->sk_backlog.tail = NULL;

		newsk->sk_userlocks	= sk->sk_userlocks & ~SOCK_BINDPORT_LOCK;



		sock_reset_flag(newsk, SOCK_DONE);