[dpdk-users] KNI Threads/Cores

Cliff Burdick shaklee3 at gmail.com
Wed Jun 8 21:48:43 CEST 2016

Hi Yigit, when you say "I guess it's possible" is that not common? I would
think that the amount of traffic people would want to forward to Linux for
normal DPDK applications would be quite small. If you had to have a core
dedicated for KNI on each interface that would get very wasteful.

On Wed, Jun 8, 2016 at 12:31 PM, Ferruh Yigit <ferruh.yigit at intel.com>

> On 6/8/2016 5:30 PM, Cliff Burdick wrote:
> > Hi, I have an application with two sockets where each core I'm planning
> to
> > transmit and receive a fairly large amount of traffic per core. Each core
> > right now handles a single queue of either TX or RX of a given port.
> Across
> > all the cores, I may be processing up to 12 ports. I also need to handle
> > things like ARP and ping, so I'm going to add in the KNI driver to handle
> > that. Since the amount of traffic I'm expecting that I'll need to forward
> > to Linux is very small, it seems like I should be able to dedicate one
> > lcore per socket to handle this functionality and have the dataplane
> cores
> > pass the traffic off to this core using rte_kni_tx_burst().
> >
> > My question is, first of all, is this possible? It seems like I can
> > configure the KNI driver to start in "single thread" mode. From that
> point,
> > I want to initialize one KNI device for each port, and have each kernel
> > lcore on each processor handle that traffic. I believe if I call
> > rte_kni_alloc with core_id set to the kernel lcore for each device, then
> in
> > the end I'll have something like 6 KNI devices on socket one being
> handled
> > by lcore 0, and 6 KNI devices on socket 2 being handled by lcore 31 as an
> > example. Then my threads that are handling the dataplane tx/rx can simply
> > be passed a pointer to their respective rte_kni device. Does this sound
> > correct?
> If rte_kni module used "single thread" mode, kernel core_id is not used
> at all. For single thread mode, a single thread created, this is used to
> for all kni devices and not able to pin to any specific lcore.
> For what you have described, first need to insert module with
> kthread_mode=multiple param. This will create a kernel thread per kni
> interface. But I guess it is possible to provide same
> rte_kni_conf->core_id for some of them, and yes rte_kni_conf->force_pin
> is required, otherwise core_id is not useful. According your sample,
> first 6 kni devices will have core_id value 0, and other 6 kni devices
> will have core_id value 31, with all have force_bind set. This will
> create 12 kernel threads, will bind 6 of them to core 0 and other 6 to
> core 31.
> >
> > Also, the sample says the core affinity needs to be set using taskset. Is
> > that already taken care of with conf.core_id in rte_kni_alloc or do I
> still
> > need to set it?
> >
> > Thanks
> >

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