[PATCH 04/13] RDS/TCP: Wait to wake thread when write space available

[Andy Grover <andy.grover@oracle.com>]

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>
---
 net/rds/tcp_send.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/rds/tcp_send.c b/net/rds/tcp_send.c
index 34fdcc0..a28b895 100644
--- 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);
 
-- 
1.6.3.3