[dpdk-dev] Survey for final decision about per-port offload API

[Ananyev, Konstantin]

Hi Ferruh,

> 
> On 3/30/2018 2:47 PM, Thomas Monjalon wrote:
> > There are some discussions about a specific part of the offload API:
> > 	"To enable per-port offload, the offload should be set on both
> > 	device configuration and queue setup."
> >
> > It means the application must repeat the port offload flags
> > in rte_eth_conf.[rt]xmode.offloads and rte_eth_[rt]xconf.offloads,
> > when calling respectively rte_eth_dev_configure() and
> > rte_eth_[rt]x_queue_setup for each queue.
> >
> > The PMD must check if there is mismatch, i.e. a port offload not
> > repeated in queue setup.
> > There is a proposal to do this check at ethdev level:
> > 	http://dpdk.org/ml/archives/dev/2018-March/094023.html
> >
> > It was also proposed to relax the API and allow "forgetting" port
> > offloads in queue offloads:
> > 	http://dpdk.org/ml/archives/dev/2018-March/092978.html
> >
> > It would mean the offloads applied to a queue result of OR operation:
> > 	rte_eth_conf.[rt]xmode.offloads | rte_eth_[rt]xconf.offloads
> >
> > 1/ Do you agree with above API change?
> 
> There is a detail of ability to disabling queue level offloads in queue_setup()
> function, I want to discuss here.
> 
> Prolog:
> port level offload: An offload only can be applied port level, to all queues.
> queue level offload: An offload can be applied into individual queues of the port
> 
> PMD reports port offload capability: port level offload + queue level offload
> PMD reports queue offload capability: queue level offload
> 
> 
> Above suggested change to API:
> - Application will be limited in configure() to set only an offload within "port
> offload capability"
> - Application will be limited in queue_setup() to set only an offload within
> "queue offload capability"
> 
> 
> This doesn't say much about disabling an offload in queue_setup(), as a rule:
> - An "port level offload" can't be disabled in queue_setup()
> 
> 
> There are two cases of disable:
> 1- Disabling a "queue level offload" enabled queue_setup() previously
> 2- Disabling a "queue level offload" enabled in configure()
> 
> If second is not supported, to disable the offload, applications should
> stop->re-configure()->re-queue_setup()->start the port. But having this
> capability makes the offloading parameters more confusing for applications.
> 
> 
> I suggest adding disable support to fist one but not second one.

Not sure why to introduce such limitation?
Konstantin