RDS/TCP: Wait to wake thread when write space available

Instead of waking the send thread whenever any send space is available,
wait until it is at least half empty. This is modeled on how
sock_def_write_space() does it, and may help to minimize context
switches.

Signed-off-by: Andy Grover <andy.grover@oracle.com>

diff --git a/net/rds/tcp_send.c b/net/rds/tcp_send.c
index ab545e0cd5d6a78da08481139158f6e87231a255..f9ee3ce087c16aad70e2d4c99f59b8cb22f79cba 100644 (file)
--- a/net/rds/tcp_send.c
+++ b/net/rds/tcp_send.c
@@ -240,7 +240,9 @@ void rds_tcp_write_space(struct sock *sk)
        tc->t_last_seen_una = rds_tcp_snd_una(tc);
        rds_send_drop_acked(conn, rds_tcp_snd_una(tc), rds_tcp_is_acked);
 
-       queue_delayed_work(rds_wq, &conn->c_send_w, 0);
+        if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf)
+               queue_delayed_work(rds_wq, &conn->c_send_w, 0);
+
 out:
        read_unlock(&sk->sk_callback_lock);