[dpdk-dev] KNI latency improvement

Stephen Hemminger stephen at networkplumber.org
Fri Dec 29 18:13:45 CET 2017


On Fri, 29 Dec 2017 15:27:03 +0100
Nirmoy Das <ndas at suse.de> wrote:

> Hi Ferruh,
> 
> There is latency in the range of milliseconds when packets are passed
> through KNI up to the IP stack. With CONFIG_RTE_KNI_PREEMPT_DEFAULT=n
> its required sacrifice a cpu core. Do you have any suggestion to improve
> latency without sacrificing a cpu?
> 
> What do you think about using cond_resched() instead of
> schedule_timeout_interruptible(), in our test it helped to reduce
> latency?
> 

That fully consumes a CPU  core when doing KNI.
It would be better to figure out how to use a a NAPI style
API for this.  I.e keep processing packet until idle,
then poll for a small window more, then if still idle
wait in kernel to be kicked by syscall from user space.


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