net: speedup sk_wake_async()
An incoming datagram must bring into cpu cache *lot* of cache lines,
in particular : (other parts omitted (hash chains, ip route cache...))
On 32bit arches :
offsetof(struct sock, sk_rcvbuf) =0x30 (read)
offsetof(struct sock, sk_lock) =0x34 (rw)
offsetof(struct sock, sk_sleep) =0x50 (read)
offsetof(struct sock, sk_rmem_alloc) =0x64 (rw)
offsetof(struct sock, sk_receive_queue)=0x74 (rw)
offsetof(struct sock, sk_forward_alloc)=0x98 (rw)
offsetof(struct sock, sk_callback_lock)=0xcc (rw)
offsetof(struct sock, sk_drops) =0xd8 (read if we add dropcount support, rw if frame dropped)
offsetof(struct sock, sk_filter) =0xf8 (read)
offsetof(struct sock, sk_socket) =0x138 (read)
offsetof(struct sock, sk_data_ready) =0x15c (read)
We can avoid sk->sk_socket and socket->fasync_list referencing on sockets
with no fasync() structures. (socket->fasync_list ptr is probably already in cache
because it shares a cache line with socket->wait, ie location pointed by sk->sk_sleep)
This avoids one cache line load per incoming packet for common cases (no fasync())
We can leave (or even move in a future patch) sk->sk_socket in a cold location
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index 1621935..98398bd 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -504,6 +504,7 @@
SOCK_TIMESTAMPING_SOFTWARE, /* %SOF_TIMESTAMPING_SOFTWARE */
SOCK_TIMESTAMPING_RAW_HARDWARE, /* %SOF_TIMESTAMPING_RAW_HARDWARE */
SOCK_TIMESTAMPING_SYS_HARDWARE, /* %SOF_TIMESTAMPING_SYS_HARDWARE */
+ SOCK_FASYNC, /* fasync() active */
};
static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
@@ -1396,7 +1397,7 @@
static inline void sk_wake_async(struct sock *sk, int how, int band)
{
- if (sk->sk_socket && sk->sk_socket->fasync_list)
+ if (sock_flag(sk, SOCK_FASYNC))
sock_wake_async(sk->sk_socket, how, band);
}