tree e439d62aa7299ad6644b37b3e569ca3de8c0f60b
parent 6f7c156c08d5eaa9fff2bd062f0a2b9d09a1e7a9
author Amos Kong <akong@redhat.com> 1307604430 -0700
committer David S. Miller <davem@davemloft.net> 1307604430 -0700

tun: do not put self in waitq if doing a nonblock read

Perf shows a relatively high rate (about 8%) race in
spin_lock_irqsave() when doing netperf between external host and
guest. It's mainly becuase the lock contention between the
tun_do_read() and tun_xmit_skb(), so this patch do not put self into
waitqueue to reduce this kind of race. After this patch, it drops to
4%.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>