Subject: [PATCH] vhost: wake up worker outside spin_lock

From: Qin Chuanyu <[email-masked]>
Date: Fri, 7 Jun 2013 21:50:16 +0800

the wake_up_process func is included by spin_lock/unlock in 
vhost_work_queue,
but it could be done outside the spin_lock.
I have test it with kernel 3.0.27 and guest suse11-sp2 using iperf,
the num as below.
                  original                 modified
thread_num  tp(Gbps)   vhost(%)  |  tp(Gbps)     vhost(%)
1           9.59        28.82    |   9.59        27.49
8           9.61        32.92    |   9.62        26.77
64          9.58        46.48    |   9.55        38.99
256         9.6         63.7     |   9.6         52.59

Signed-off-by: Chuanyu Qin <[email-masked]>
---
  drivers/vhost/vhost.c |    4 +++-
  1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 94dbd25..dcc7a17 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -146,9 +146,11 @@ static inline void vhost_work_queue(struct 
vhost_dev *dev,
  	if (list_empty(&work->node)) {
  		list_add_tail(&work->node, &dev->work_list);
  		work->queue_seq++;
+		spin_unlock_irqrestore(&dev->work_lock, flags);
  		wake_up_process(dev->worker);
+	} else {
+		spin_unlock_irqrestore(&dev->work_lock, flags);
  	}
-	spin_unlock_irqrestore(&dev->work_lock, flags);
  }

  void vhost_poll_queue(struct vhost_poll *poll)
-- 
1.7.3.1.msysgit.0