Hi Ilya,

> Hi,

>
> Hi, Alessandro.
>
> >
> >   My name is Alessandro Rosetti, and I'm currently adding netmap support
> to
> > ovs, following an approach similar to DPDK.
>
> Good to know that someone started to work on this. IMHO, it's a good idea.
> I also wanted to try to implement this someday, but had no much time.
>
> >
> > I've created a new netdev: netdev_netmap that uses the pmd
> infrastructure.
> > The prototype I have seems to work fine (I still need to tune
> performance,
> > test optional features, and test more complex topologies.)
>
> Cool. Looking forward for your RFC patch-set.
>
> >
> > I have a question about the lifetime of dp_packets.
> > Is there any guarantee that the dp_packets allocated in a receive
> callback
> > (e.g. netdev_netmap_rxq_recv) are consumed by OVS (e.g. dropped, cloned,
> or
> > sent to other ports) **before** a subsequent call to the receive callback
> > (on the same port)?
> > Or is it possible for dp_packets to be stored somewhere (e.g. in an OVS
> > internal queue) and live across subsequent invocations of the receive
> > callback that allocated them?
>
> I think that there was never such a guarantee, but recent changes in
> userspace
> datapath completely ruined this assumption. I mean output packet batching
> support.
>
> Please refer the following commits for details:
> 009e003 2017-12-14 | dpif-netdev: Output packet batching.
> c71ea3c 2018-01-15 | dpif-netdev: Time based output batching.
> 00adb8d 2018-01-15 | docs: Describe output packet batching in DPDK guide.
>

Thanks a lot for for the quick reply. So we will add a dp_packet allocator
for netmap.
Is there is any guarantee that a dp_packet allocated by a PMD thread will
be deallocated
by the same thread and only the same thread? At first glance it seems this
is the case...

Thanks,
  Vincenzo


>
> >
> > I need to know if this is the case to check that my current prototype is
> > safe.
> > I use per-port pre-allocation of dp_packets, for maximum performance.
> I've
> > seen that DPDK uses its internal allocator to allocate and deallocate
> > dp_packets, but netmap does not expose one.
> > Each packet received with netmap is created as a new type dp_packet:
> > DPBUF_NETMAP. The data points to a netmap buffer (preallocated by the
> > kernel).
> > When I receive data (netdev_netmap_rxq_recv) I reuse the dp_packets,
> > updating the internal pointer and a couple of additional informations
> > stored inside the dp_packet.
> > When I have to send data I use zero copy if dp_packet is DPBUF_NETMAP and
> > copy if it's not.
> >
> > Thanks for the help!
> > Alessandro.
>
>
>
>


-- 
Vincenzo Maffione
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