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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 /drivers/net/tun.c
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>
Diffstat (limited to 'drivers/net/tun.c')
-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 4cda69b6b28..3f0cdc14be8 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);
}