Re: [dpdk-dev] eventdev: sw rx adapter enqueue caching

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

> 
> Hi,
> 
> The SW eventdev rx adapter has an internal enqueue buffer 'rx_adapter-
> >event_enqueue_buffer', which stores packets received from the NIC until at
> least BATCH_SIZE (=32) packets have been received before enqueueing them
> to eventdev. For example in case of validation testing, where often a small
> number of specific test packets is sent to the NIC, this causes a lot of
> problems. One would always have to transmit at least BATCH_SIZE test
> packets before anything can be received from eventdev. Additionally, if the rx
> packet rate is slow this also adds a considerable amount of additional delay.
> 
> Looking at the rx adapter API and sw implementation code there doesn’t
> seem to be a way to disable this internal caching. In my opinion this
> “functionality" makes testing sw rx adapter so cumbersome that either the
> implementation should be modified to enqueue the cached packets after a
> while (some performance penalty) or there should be some method to
> disable caching. Any opinions how this issue could be fixed?
At the minimum, I would think there should be a compile time option.
From a use case perspective, I think it falls under latency vs throughput considerations. If there is a latency sensitive application, it might not want to wait till 32 packets are received.

> 
> 
> Regards,
> Matias