On 08.02.2018 17:21, Vincenzo Maffione wrote: > 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...
Hi Vincenzo, I would prefer that you do not make such assumptions. Even if it works now, netdev abstraction layer doesn't guarantee that. It states that 'rxq_recv()' function of netdev-provider "stores pointers to up to NETDEV_MAX_BURST dp_packets into the array, transferring ownership of the packets to the caller". This means that caller is able to do anything with received dp_packets including but not limited to queueing or transferring to another thread. > > 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 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
