From 8e82376e5f72bb576504c8c6117685e56c1b97db Mon Sep 17 00:00:00 2001
From: Andy Grover <andy.grover@oracle.com>
Date: Thu, 11 Mar 2010 13:49:58 +0000
Subject: 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>
Signed-off-by: David S. Miller <davem@davemloft.net>

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);
 
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