[dpdk-dev] [PATCH 1/2] eventdev: add event adapter for ethernet Rx queues

[Eads, Gage]

> -----Original Message-----
> From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com]
> Sent: Wednesday, August 9, 2017 11:20 AM
> To: Eads, Gage <gage.eads at intel.com>
> Cc: Rao, Nikhil <nikhil.rao at intel.com>; dev at dpdk.org; thomas at monjalon.net;
> Richardson, Bruce <bruce.richardson at intel.com>; Van Haaren, Harry
> <harry.van.haaren at intel.com>; hemant.agrawal at nxp.com;
> nipun.gupta at nxp.com; Vangati, Narender <narender.vangati at intel.com>;
> Gujjar, Abhinandan S <abhinandan.gujjar at intel.com>
> Subject: Re: [PATCH 1/2] eventdev: add event adapter for ethernet Rx queues
> 
> -----Original Message-----
> > Date: Wed, 9 Aug 2017 02:23:15 +0000
> > From: "Eads, Gage" <gage.eads at intel.com>
> > To: Jerin Jacob <jerin.jacob at caviumnetworks.com>
> > CC: "Rao, Nikhil" <nikhil.rao at intel.com>, "dev at dpdk.org"
> > <dev at dpdk.org>,  "thomas at monjalon.net" <thomas at monjalon.net>,
> "Richardson, Bruce"
> >  <bruce.richardson at intel.com>, "Van Haaren, Harry"
> >  <harry.van.haaren at intel.com>, "hemant.agrawal at nxp.com"
> >  <hemant.agrawal at nxp.com>, "nipun.gupta at nxp.com"
> > <nipun.gupta at nxp.com>,  "Vangati, Narender"
> <narender.vangati at intel.com>, "Gujjar, Abhinandan S"
> >  <abhinandan.gujjar at intel.com>
> > Subject: RE: [PATCH 1/2] eventdev: add event adapter for ethernet Rx
> > queues
> >
> >
> >
> > > -----Original Message-----
> > > From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com]
> > > Sent: Thursday, August 3, 2017 1:23 AM
> > > To: Eads, Gage <gage.eads at intel.com>
> > > Cc: Rao, Nikhil <nikhil.rao at intel.com>; dev at dpdk.org;
> > > thomas at monjalon.net; Richardson, Bruce <bruce.richardson at intel.com>;
> > > Van Haaren, Harry <harry.van.haaren at intel.com>;
> > > hemant.agrawal at nxp.com; nipun.gupta at nxp.com; Vangati, Narender
> > > <narender.vangati at intel.com>; Gujjar, Abhinandan S
> > > <abhinandan.gujjar at intel.com>
> > > Subject: Re: [PATCH 1/2] eventdev: add event adapter for ethernet Rx
> > > queues
> > >
> > > -----Original Message-----
> > > > Date: Wed, 2 Aug 2017 19:19:32 +0000
> > > > From: "Eads, Gage" <gage.eads at intel.com>
> > > > To: Jerin Jacob <jerin.jacob at caviumnetworks.com>, "Rao, Nikhil"
> > > >  <nikhil.rao at intel.com>
> > > > CC: "dev at dpdk.org" <dev at dpdk.org>, "thomas at monjalon.net"
> > > >  <thomas at monjalon.net>, "Richardson, Bruce"
> > > > <bruce.richardson at intel.com>,  "Van Haaren, Harry"
> > > <harry.van.haaren at intel.com>, "hemant.agrawal at nxp.com"
> > > >  <hemant.agrawal at nxp.com>, "nipun.gupta at nxp.com"
> > > > <nipun.gupta at nxp.com>,  "Vangati, Narender"
> > > <narender.vangati at intel.com>, "Gujjar, Abhinandan S"
> > > >  <abhinandan.gujjar at 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?
> >
> > It could be. Thinking on it some more, I'm a little concerned about doing
> configuration without the application's knowledge. Possible issues that could
> arise:
> > - The user later reconfigures the event device with fewer ports and
> > the adapter's port becomes invalid, or reconfigures it with more ports
> > and begins using the port the adapter is using
> > - rte_event_port_count() + 1 extends beyond the PMD's capabilities
> > (the sw PMD is hard-coded to support a max of 64 ports, for example)
> >
> > Having the user be responsible for the port configuration could avoid these
> problems. Since the user needs to check the <eventdev, ethdev> pair's
> capabilities for the CAP_ADD_QUEUE anyway, they could also check for
> INBUILT_PORT and decide whether or not to request an additional port at
> eventdev configure time -- thereby ensuring they don't waste a port when using
> hardware with inbuilt ports. And this keeps the configuration code in one place
> (the app), rather than spread across the app, adapter, and potentially the
> conf_cb.
> 
> OK.Sounds reasonable.May be we can push the responsibility to application.We
> could have a helper function using the proposed adapter API. That helper
> function would create the adapter based on the capability for the _default_
> case.
> Applications free to use the raw adapter API to get more control if required.
> Otherwise we will duplicate the code in all the applications.
>

Makes sense. Are you thinking the helper function would do stop + reconfig with additional port + start + setup port, or just setup the port with an ID the app supplies (only when a port is required, of course)? The second one could be done with little additional code -- the app just needs to check if an additional port is needed when configuring the eventdev, and another helper function could take a list of <eventdev, ethdev> pairs and return true if any don't have an inbuilt port.