Re: [dpdk-dev] [PATCH RFC 0/3] DPDK ethdev callback support

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Hi Bruce,

Callbacks, as hooks for applications, give more flexibility and are
generally a good idea.
In DPDK the main issue will be to avoid performance degradation.
I see you use "unlikely" for callback branching.
Could we reduce more the impact of this test by removing the queue array,
i.e. having port-wide callbacks instead of per-queue callbacks?

2014-12-22 16:47, Bruce Richardson:
> Future extensions: in future the ethdev library can be extended to provide
> a standard set of callbacks for use by drivers. 

Having callbacks for drivers seems strange to me.
If drivers need to accomplish some tasks, they do it by implementing an
ethdev service. New services are declared for new needs.
Callbacks are the reverse logic. Why should it be needed?

> For now this patch set is RFC and still needs additional work for creating
> a remove function for callbacks and to add in additional testing code.
> Since this adds in new code into the critical data path, I have run some
> performance tests using testpmd with the ixgbe vector drivers (i.e. the
> fastest, fast-path we have :-) ). Performance drops due to this patch
> seems minimal to non-existant, rough tests on my system indicate a drop
> of perhaps 1%.
> 
> All feedback welcome.

It would be good to have more performance tests with different configurations.

Thanks
-- 
Thomas