[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/netfront: handle compound page fragments on transmit
On Tue, 2012-11-20 at 15:28 +0000, Eric Dumazet wrote: > On Tue, 2012-11-20 at 15:06 +0000, Ian Campbell wrote: > > > In practice no because of the property that the number of pages backing > > the frags is <= MAX_SKB_FRAGS even if you are using compound pages as > > the frags. > > Yes, but you can make this test trigger with some hacks from userland > (since the frag allocator is per task instead of per socket), so you > should remove the dump_stack() ? > > Best way would be to count exact number of slots. > > This could be something like 48 slots for a single skb > > (if each frag is 4098 (1+4096+1)bytes, only the last one is around 4000 > bytes) > > MAX_SKB_FRAGS is really number of frags, while your driver needs a count > of 'order-0' 'frames' The use of MAX_SKB_FRAGS is a bit misleading here, it's really the max number of slots which the other end will be willing to receive as a single frame (in the Ethernet sense), as defined by the PV protocol. It happens to be the same as MAX_SKB_FRAGS (or it is at least MAX_SKB_FRAGS, I'm not too sure). I'll nuke the dump_stack() though -- it's not clear what sort of useful context it would contain anyway. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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