[dpdk-dev] drops while transmitting to the kni using rte_kni_tx_burst()

[Ferruh Yigit]

On 1/16/2017 2:58 PM, Shirley Avishour wrote:
> I am currently using the kernel interface for recording the received
> traffic by duplicating the received packets and sending a copy to the
> kni (and performing pcap_open_live on the kni).
> my goal rate is around 500Mbps. is it possible to achieve it via the kni ??

According quick experiment,
- with kni module lo_mode_fifo_skb (which send all received packets to
tx, but allocating and copying data to skb to be more realistic)
- single kernel thread
- kernel thread bind to a core
- using kni sample app
- With small packets

Best numbers get when rx,tx and kernel cores are in same socket with the
NIC, it is ~1.7Mpps (million packet per second)

When KNI_RX_LOOP_NUM increased to 10000, it becomes ~1.9Mpps.

> 
> 
> On Mon, Jan 16, 2017 at 4:55 PM, Ferruh Yigit <ferruh.yigit at intel.com
> <mailto:ferruh.yigit at intel.com>> wrote:
> 
>     On 1/16/2017 2:47 PM, Shirley Avishour wrote:
>     > Hi,
>     > As I wrote the kernel thread runs on a dedicated lcore.
>     > running top while my application is running I see kni_single and the cpu
>     > usage is really low...
>     > Is there any rate limitation for transmitting to the kernel interface
>     > (since packets are being copied in the kernel).
> 
>     Yes, kind of, kernel thread sleeps periodically, with a value defined by
>     KNI_KTHREAD_RESCHEDULE_INTERVAL. You can try tweaking this value, if you
>     want thread do more work, less sleep J
> 
>     Also KNI_RX_LOOP_NUM can be updated for same purpose.
> 
>     >
>     >
>     > On Mon, Jan 16, 2017 at 4:42 PM, Ferruh Yigit <ferruh.yigit at intel.com <mailto:ferruh.yigit at intel.com>
>     > <mailto:ferruh.yigit at intel.com <mailto:ferruh.yigit at intel.com>>>
>     wrote:
>     >
>     >     On 1/16/2017 12:20 PM, Shirley Avishour wrote:
>     >     > Hi,
>     >     > I have an application over dpdk which is consisted of the
>     following threads
>     >     > each running on a separate core:
>     >     > 1) rx thread which listens on in a poll mode for traffic
>     >     > 2) 2 packet processing threads (for load balancing)
>     >     > 3) kni thread (which also runs on a separate core).
>     >
>     >     This is kernel thread, right? Is it bind to any specific core?
>     >     Is it possible that this thread shares the core with 2nd
>     processing
>     >     thread when enabled?
>     >
>     >     >
>     >     > the rx thread receives packets and clones them and transmit
>     a copy
>     >     to the
>     >     > kni and the other packet is sent to the packet processing unit
>     >     (hashing
>     >     > over 2 threads).
>     >     > the receive traffic rate is 100Mbps.
>     >     > When working with single packet processing thread I am able
>     to get
>     >     all the
>     >     > 100Mbps towards the kni with no drops.
>     >     > but when I activate my application with 2 packet processing
>     >     threads I start
>     >     > facing drops towards the kni.
>     >     > the way I see it the only difference now is that I have another
>     >     threads
>     >     > which handles an mbuf and frees it once processing is completed.
>     >     > Can anyone assist with this case please?
>     >     >
>     >     > Thanks!
>     >     >
>     >
>     >
> 
>