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authorHerbert Xu <herbert@gondor.apana.org.au>2009-06-03 21:45:55 -0700
committerDavid S. Miller <davem@davemloft.net>2009-06-03 21:45:55 -0700
commitc722c625dbe2758d53365c0ed7d401b0e286f2cf (patch)
tree4b73bc0edf80e3b5652c35512fbdb19f472b557a
parenta8c617eae4dc2ea9f3d64472233f2d3dc3c9993c (diff)
tun: Only wake up writers
When I added socket accounting to tun I inadvertently introduced spurious wake-up events that kills qemu performance. The problem occurs when qemu polls on the tun fd for read, and then transmits packets. For each packet transmitted, we will wake up qemu even if it only cares about read events. Now this affects all sockets, but it is only a new problem for tun. So this patch tries to fix it for tun first and we can then look at the problem in general. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/tun.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4cda69b6b28c..3f0cdc14be82 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -844,12 +844,12 @@ static void tun_sock_write_space(struct sock *sk)
if (!sock_writeable(sk))
return;
- if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
- wake_up_interruptible_sync(sk->sk_sleep);
-
if (!test_and_clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags))
return;
+ if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
+ wake_up_interruptible_sync(sk->sk_sleep);
+
tun = container_of(sk, struct tun_sock, sk)->tun;
kill_fasync(&tun->fasync, SIGIO, POLL_OUT);
}