linux-kernel - Re: [PATCH 6/6] vhost_net: don't poll on -EFAULT

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Message-ID: <20120416071646.GB25396@redhat.com>
Date:	Mon, 16 Apr 2012 10:16:47 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	netdev@...r.kernel.org, xma@...ibm.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org, ebiederm@...ssion.com
Subject: Re: [PATCH 6/6] vhost_net: don't poll on -EFAULT

On Mon, Apr 16, 2012 at 02:08:33PM +0800, Jason Wang wrote:
> Currently, we restart tx polling unconditionally when sendmsg()
> fails. This would cause unnecessary wakeups of vhost wokers as it's
> only needed when the socket send buffer were exceeded.

Why is this a problem?

> Fix this by
> restart the tx polling only when sendmsg() returns value other than
> -EFAULT.
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/vhost/net.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 29abd65..035fa95 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -262,7 +262,8 @@ static void handle_tx(struct vhost_net *net)
>  					UIO_MAXIOV;
>  			}
>  			vhost_discard_vq_desc(vq, 1);
> -			tx_poll_start(net, sock);
> +			if (err != -EFAULT)
> +				tx_poll_start(net, sock);
>  			break;
>  		}
>  		if (err != len)
--
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