[dpdk-dev] Question on the Ring Library

[François-Frédéric Ozog]

You are welcome !

 

Even if you insert packets in batch into a fifo, the mutex is still
unpredictable. If one pthread_lock costs 1ms, you are going to lose packets,
regardless of the number of RSS queues and ring sizes
 Batching comes with
another issue: need to flush a batch after a certain timeout if you do not
have packets. Userland timer resolution is such that you are introducing
port to port latency quite a lot: DPDK native, you can manage to get a 2µs
latency (including PCI express), while with batch it may be 1ms
 You may
find smarter algorithms but still you will be an order of magnitude higher
than DPDK.

 

Hope this helps.

 

François-Frédéric

 

De : Sambath Kumar Balasubramanian
[mailto:sambath.balasubramanian at gmail.com] 
Envoyé : mercredi 4 décembre 2013 15:01
À : François-Frédéric Ozog
Cc : dev at dpdk.org
Objet : Re: [dpdk-dev] Question on the Ring Library

 

Thanks François-Frédéric. That puts real good perspective on the cost for
the vent assuming each packet in the fast will result

in an event. If event rate is orders of magnitude less than the packet rate,
then I guess we can still achieve 10G since the "extra cost" will be in the
event thread and not in the fast path thread.

 

Regards,

Sambath