Re: [Xen-devel] [PATCH net] xen-netback: Fix handling of skbs requiring too many slots

[annie li <annie.li@xxxxxxxxxx>]

On 2014/6/4 11:42, Zoltan Kiss wrote:
> On 04/06/14 16:09, annie li wrote:
> > On 2014/6/3 16:30, Zoltan Kiss wrote:
> > > A recent commit (a02eb4 "xen-netback: worse-case estimate in
> > > xenvif_rx_action is
> > > underestimating") capped the slot estimation to MAX_SKB_FRAGS, but
> > > that triggers
> > > the next BUG_ON a few lines down, as the packet consumes more slots 
> > > than
> > > estimated.
> > > This patch introduces full_coalesce on the skb callback buffer, which
> > > is used in
> > > start_new_rx_buffer() to decide whether netback needs coalescing more
> > > aggresively. By doing that, no packet should need more than
> > > XEN_NETIF_MAX_TX_SIZE / PAGE_SIZE data slots,
> > (XEN_NETIF_MAX_TX_SIZE+1) / PAGE_SIZE here?
> Do you think about the GSO slot? That's why I wrote "data slot", 
> however that's probably not a clear terminology.
What I mean is: XEN_NETIF_MAX_TX_SIZE is 0xFFFF, and 
XEN_NETIF_MAX_TX_SIZE / PAGE_SIZE turns out to be 15 slots when 
PAGE_SIZE is 4096. You was trying to use XEN_NETIF_MAX_TX_SIZE as max 
size of packet - 64k?
> I'll add then that excluding GSO slot, as it doesn't carry data 
> directly, therefore it's irrelevant from this point of view.
Correct.:-)

Thanks
Annie
> Zoli
>
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