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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Nov 28, 2013 at 04:33:53PM +0000, Paul Durrant wrote:
> > -----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.
> 

I guess this would work.

Wei.

>   Paul

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