Re: [Xen-devel] [PATCH net-next] xen-netback: improve guest-receive-side flow control

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: David Vrabel
> Sent: 02 December 2013 11:52
> To: Paul Durrant
> Cc: xen-devel@xxxxxxxxxxxxx; Wei Liu; Ian Campbell
> Subject: Re: [PATCH net-next] xen-netback: improve guest-receive-side flow
> control
> 
> On 28/11/13 13:11, Paul Durrant wrote:
> > The flow control code relies on a double pass of tke skb, firstly to count
> > the number of ring slots needed to supply sufficient grant references, and
> > another to actually consume those references and build the grant copy
> > operations. It transpires that, in some scenarios, the initial count and the
> > number of references consumed differs and, after this happens a number
> of
> > times, flow control is completely broken.
> 
> Can you describe in more detail the cases where it gets it wrong?
> 

I've already elaborated on this thread (at Annie Li's request). That 
explanation is probably a little long for inclusion in the comment though.

> > -unsigned int xenvif_count_skb_slots(struct xenvif *vif, struct sk_buff
> *skb)
> 
> Any patch that gets rid of this gets my vote (provided it works!).
> 
> Can you list all the guest frontends that you've tested this with?
> 

So, far a couple of windows guests for dev test purposes, but it is going 
through XenRT too which will exercise linux guests too.

  Paul

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