[dpdk-dev] [PATCH 4/4] ethdev: add helpers to move to the new offloads API

Ananyev, Konstantin konstantin.ananyev at intel.com
Mon Sep 4 16:18:25 CEST 2017



> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas at monjalon.net]
> Sent: Monday, September 4, 2017 2:54 PM
> To: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> Cc: Shahaf Shuler <shahafs at mellanox.com>; dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH 4/4] ethdev: add helpers to move to the new offloads API
> 
> 04/09/2017 15:25, Ananyev, Konstantin:
> > Hi Shahaf,
> >
> > > +/**
> > > + * A conversion function from rxmode offloads API to rte_eth_rxq_conf
> > > + * offloads API.
> > > + */
> > > +static void
> > > +rte_eth_convert_rxmode_offloads(struct rte_eth_rxmode *rxmode,
> > > +				struct rte_eth_rxq_conf *rxq_conf)
> > > +{
> > > +	if (rxmode->header_split == 1)
> > > +		rxq_conf->offloads |= DEV_RX_OFFLOAD_HEADER_SPLIT;
> > > +	if (rxmode->hw_ip_checksum == 1)
> > > +		rxq_conf->offloads |= DEV_RX_OFFLOAD_CHECKSUM;
> > > +	if (rxmode->hw_vlan_filter == 1)
> > > +		rxq_conf->offloads |= DEV_RX_OFFLOAD_VLAN_FILTER;
> >
> > Thinking on it a bit more:
> > VLAN_FILTER is definitely one per device, as it would affect VFs also.
> > At least that's what we have for Intel devices (ixgbe, i40e) right now.
> > For Intel devices VLAN_STRIP is also per device and
> > will also be  applied to all corresponding VFs.
> > In fact, right now it is possible to query/change these 3 vlan offload flags on the fly
> > (after dev_start) on  port basis by rte_eth_dev_(get|set)_vlan_offload API.
> > So, I think at least these 3 flags need to be remained on a port basis.
> 
> I don't understand how it helps to be able to configure the same thing
> in 2 places.

Because some offloads are per device, another - per queue.
Configuring on a device basis would allow most users to conjure all
queues in the same manner by default.
Those users who would  need more fine-grained setup (per queue)
will be able to overwrite it by rx_queue_setup().
 
> I think you are just describing a limitation of these HW: some offloads
> must be the same for all queues.

As I said above - on some devices some offloads might also affect queues
that belong to VFs (to another ports in DPDK words).   
You might never invoke rx_queue_setup() for these queues per your app.
But you still want to enable this offload on that device.

> It does not prevent from configuring them in the per-queue setup.
> 
> > In fact, why can't we have both per port and per queue RX offload:
> > - dev_configure() will accept RX_OFFLOAD_* flags and apply them on a port basis.
> > - rx_queue_setup() will also accept RX_OFFLOAD_* flags and apply them on a queue basis.
> > - if particular RX_OFFLOAD flag for that device couldn't be setup on a queue basis  -
> >    rx_queue_setup() will return an error.
> 
> The queue setup can work while the value is the same for every queues.

Ok, and how people would know that?
That for device N offload X has to be the same for all queues,
and for device M offload X can be differs for different queues.

Again, if we don't allow to enable/disable offloads for particular queue,
why to bother with updating rx_queue_setup() API at all? 

> 
> > - rte_eth_rxq_info can be extended to provide information which RX_OFFLOADs
> >   can be configured on a per queue basis.
> 
> Yes the PMD should advertise its limitations like being forced to
> apply the same configuration to all its queues.

Didn't get your last sentence.
Konstantin

> 
> > BTW - in that case we probably wouldn't need ignore flag inside rx_conf anymore.



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