Re: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx offloads API

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Qi,

> -----Original Message-----
> From: Zhang, Qi Z
> Sent: Thursday, March 29, 2018 10:51 AM
> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>; Dai, Wei <wei.dai@intel.com>; Wang, Xiao W <xiao.w.wang@intel.com>
> Cc: 'dev@dpdk.org' <dev@dpdk.org>
> Subject: RE: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx offloads API
> 
> Hi Konstantin:
> 
> > -----Original Message-----
> > From: Ananyev, Konstantin
> > Sent: Thursday, March 29, 2018 5:29 PM
> > To: Zhang, Qi Z <qi.z.zhang@intel.com>; Dai, Wei <wei.dai@intel.com>; Wang,
> > Xiao W <xiao.w.wang@intel.com>
> > Cc: 'dev@dpdk.org' <dev@dpdk.org>
> > Subject: RE: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx
> > offloads API
> >
> >
> >
> > > -----Original Message-----
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zhang, Qi Z
> > > Sent: Thursday, March 29, 2018 7:09 AM
> > > To: Dai, Wei <wei.dai@intel.com>; Wang, Xiao W <xiao.w.wang@intel.com>
> > > Cc: 'dev@dpdk.org' <dev@dpdk.org>
> > > Subject: Re: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx
> > > offloads API
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Zhang, Qi Z
> > > > Sent: Wednesday, March 28, 2018 6:08 PM
> > > > To: Dai, Wei <wei.dai@intel.com>; Wang, Xiao W
> > > > <xiao.w.wang@intel.com>
> > > > Cc: dev@dpdk.org
> > > > Subject: RE: [PATCH v2 1/2] net/fm10k: convert to new Rx offloads
> > > > API
> > > >
> > > > Hi Daiwei:
> > > >
> > > > > +static uint64_t fm10k_get_rx_queue_offloads_capa(struct
> > > > > +rte_eth_dev
> > > > > +*dev) {
> > > > > +	RTE_SET_USED(dev);
> > > > > +
> > > > > +	return (uint64_t)(DEV_RX_OFFLOAD_SCATTER);
> > > > > +}
> > > >
> > > > why per queue rx scattered feature here?
> > > > My understanding is either we use scattered rx function that enable
> > > > this feature for all queues or we use non-scattered rx function that
> > > > disable this feature for all queues, right?
> > >
> > > Checked with Dai Wei offline, fm10k have per queue register that can
> > > be configured to support rx scattered, So it is per queue offload.
> >
> > Ok, but these days we have one RX function per device.
> > Looking at fm10k - it clearly has different RX function for scattered and
> > non-scattered case.
> > Yes, HW does support scatter/non-scatter selection per queue, but our SW -
> > doesn't (same for ixgbe and i40e) So how it could be per queue offload?
> 
> We saw the implementation of fm10k is a little bit different with i40e.
> It set per queue register "FM10K_SRRCTL_BUFFER_CHAINING_EN" to turn on multi-seg feature when offload is required.
> 
> That means two queues can have different behavior when process a packet that exceed the buffer size base on the register setting,
> though we use the same rx scattered function, so we think this is per queue feature, is that make sense?

Ok, suppose we have 2 functions configured.
One with DEV_RX_OFFLOAD_SCATTER is on, second with DEV_RX_OFFLOAD_SCATTER is off.
So scatter RX function will be selected, but for second queue  HW support will not be enabled,
so packets bigger then RX buffer will be silently dropped by HW, right?
Konstantin

> 
> Regards
> Qi
> 
> 
> > Konstantin
> 
> 
> >
> > > >
> > > > Regards
> > > > Qi