Re: eventdev: method for finding out unlink status

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Fri, 10 Aug 2018 14:24:02 +0000
> From: "Elo, Matias (Nokia - FI/Espoo)" <matias.elo@nokia.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> CC: "Van Haaren, Harry" <harry.van.haaren@intel.com>, "dev@dpdk.org"
>  <dev@dpdk.org>
> Subject: Re: [dpdk-dev] eventdev: method for finding out unlink status
> x-mailer: Apple Mail (2.3445.9.1)
> 
> 
> >
> > # Other than that, I am still not able to understand, why not
> > application wait until rte_event_port_unlink() returns.
> 
> Making rte_event_port_unlink() blocking would be troublesome if one doesn’t care
> about unlink completion. E.g. doing dynamic load balancing.

By making it as blocking(i.e the rte_event_port_unlink() returns when
unlink() completed) forcing everyone to care about unlink completion.
Right?

> 
> >
> > # What in real word use case, application can, do other than waiting
> > to complete rte_event_port_unlink(). If we try to put some logic in like,
> >
> > while (rte_event_port_unlink_in_progress(dev, port) > 0){
> >       do_something();
> > }
> >
> > The do_something() will not be called in some platform at all.
> >
> > # Any idea on what will be the real world use case, where rte_event_port_unlink() called in fastpath?
> 
> In our application this could be used for example to pause scheduling of new events while
> working on an “expensive” event to minimise delays. It is also needed when destroying
> queues, though calling this fast path is debatable (our application enables creating /
> destroying queues at runtime).

If I understand it correctly, Your current issue is, SW driver is
not waiting for to complete the unlink() operation so that in your application you are
seeing some abnormalities.

> 
> These are perhaps not the best examples but I would be very cautious to make a function
> blocking if there is even a small probability that it could be called from the fast path.

Let assume even if it is called in fastpath, what else, we can really do
other that calling rte_pause() in loop. realistically? after issuing
unlink() operation.

>