Subject: Re: Network performance with small packets - continued

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 9 Mar 2011 19:16:03 +0200

On Wed, Mar 09, 2011 at 08:51:33AM -0800, Shirley Ma wrote:
> On Wed, 2011-03-09 at 10:09 -0600, Tom Lendacky wrote:
> > > > Vhost is receiving a lot of notifications for packets that are to
> > be
> > > > transmitted (over 60% of the packets generate a kick_notify). 
> 
> This is guest TX send notification when vhost enables notification.
> 
> In TCP_STREAM test, vhost exits from reaching NAPI WEIGHT,

You mean virtio?

> it rarely
> enables the notification, vhost re-enters handle_tx from NAPI poll,

Does NAPI really call handle_tx? Not rx?

> so
> guest doesn't do much kick_notify.
> 
> In multiple TCP_RR test, seems vhost exits from nothing to send in TX vq
> very often, so it enables notification most of the time.
> 
> Shirley