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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx]
> Sent: 28 November 2013 16:27
> To: Paul Durrant
> Cc: Wei Liu; xen-devel@xxxxxxxxxxxxx; Ian Campbell; David Vrabel
> Subject: Re: [PATCH net-next] xen-netback: improve guest-receive-side flow
> control
[snip]

> > > I'm afraid this starting point is not correct. Consider you have a SKB
> > > with very large linear buffer, you might need more than 2 slots to fit
> > > that in, right?
> > >
> >
> > I was wondering about that. Would a roundup of mtu to the nearest 4k
> boundary be sufficient?
> >
> 
> I think we can reuse the logic in xenvif_gop_skb, there's a snippet used
> to calculate how many slots are necessary for linear area. We just need
> to avoid pulling requrests from the ring.
> 

Actually, DIV_ROUND(skb_headlen(skb), PAGE_SIZE) should give a cheap upper 
bound, shouldn't it? I don't want the code here to get too complex.

  Paul


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