Re: [PATCH 1/2] eventdev: add event adapter for ethernet Rx queues

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

-----Original Message-----
> Date: Wed, 2 Aug 2017 19:19:32 +0000
> From: "Eads, Gage" <gage.eads@intel.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>, "Rao, Nikhil"
>  <nikhil.rao@intel.com>
> CC: "dev@dpdk.org" <dev@dpdk.org>, "thomas@monjalon.net"
>  <thomas@monjalon.net>, "Richardson, Bruce" <bruce.richardson@intel.com>,
>  "Van Haaren, Harry" <harry.van.haaren@intel.com>, "hemant.agrawal@nxp.com"
>  <hemant.agrawal@nxp.com>, "nipun.gupta@nxp.com" <nipun.gupta@nxp.com>,
>  "Vangati, Narender" <narender.vangati@intel.com>, "Gujjar, Abhinandan S"
>  <abhinandan.gujjar@intel.com>
> Subject: RE: [PATCH 1/2] eventdev: add event adapter for ethernet Rx queues
> 
> 
> <snip>
> 
> > > >
> > > > 5) specifying rte_event_eth_rx_adapter_conf.rx_event_port_id on
> > > > rte_event_eth_rx_adapter_create() would waste one HW eventdev port
> > > > if its happen to be used RX_ADAPTER_CAP_INBUILT_PORT on
> > rte_event_eth_rx_adapter_queue_add().
> > > > unlike SW eventdev port, HW eventdev ports are costly so I think, We
> > > > need to have another eventdev PMD ops to create service/producer ports.
> > > > Or any other scheme that creates
> > > > rte_event_eth_rx_adapter_conf.rx_event_port_id
> > > > on demand by common code.
> > > >
> > >
> > > One solution is:
> > >
> > > struct rte_event_eth_rx_adapter_conf {
> > >     uint8_t dev_id;
> > >
> > >     int (*conf_cb)(uint8_t id, uint8_t port_id, uint32_t flags, struct
> > > rte_event_eth_rx_adapter_conf *conf);
> > >
> > >     unsigned int max_nb_rx;
> > >
> > >     int event_port_id;
> > >
> > >     char service_name[];
> > > }
> > >
> > > Where dev_id and conf_cb have to be specified in the create call, but
> > > event_port_id and service_name will be filled in when conf_cb() is
> > > invoked
> > 
> > I was thinking like event_port_id will be rte_event_port_count() + 1.
> > ie When adapter needs the additional port, It can
> > - stop the eventdev
> > - reconfigure with rte_event_queue_count() , rte_event_port_count() + 1
> > - start the eventdev.
> > 
> > The only problem with callback is that all the application needs to implement it.
> > If you think, application need more control then we can expose callback and if it
> > is NULL then default handler can be called in common code.
> > 
> 
> I don't think we can rely on there being another port available -- a user may have configured the sw eventdev with all 64 ports, for instance.

On that case, irrespective any scheme(callback vs non callback) the
adapter creation would fail. Right?

> What if the user is required to calculate cfg.nb_event_ports as a function of the RX_ADAPTER_CAP_INBUILT_PORT capability (i.e. add a port if the capability is not set), such that a reconfigure is not required?

We have only one NON INBUILT eventdev port per adapter. Right? i.e in the v1 spec it was rte_event_eth_rx_adapter_conf.event_port_id,
How about it can be rte_event_port_count() + 1 ? Since we are NOT
linking this port, the context call be kept in adapter itself. Right?
> 
> As for application control: that would be a useful option in the conf_cb scheme. Some apps will want to configure the adapter's port (its new_event_threshold, its queue depths) differently from the default.

struct rte_event_port_conf * can be passed on the adapter create if
application needs more control.

> 
> Thanks,
> Gage