Re: [dpdk-dev] [PATCH] net/ena: enable multi segment in Tx offload flags

["Michał Krawczyk" <mk@semihalf.com>]

śr., 28 lip 2021 o 16:27 Olivier Matz <olivier.matz@6wind.com> napisał(a):
>
> Hi Michał,
>
> On Wed, Jul 14, 2021 at 12:02:32PM +0200, Michał Krawczyk wrote:
> > pon., 12 lip 2021 o 19:03 Ghalem Boudour <ghalem.boudour@6wind.com> napisał(a):
> > >
> > > The DPDK ENA driver does not provide multi-segment tx offload capability.
> > > Let's add DEV_TX_OFFLOAD_MULTI_SEGS to ports offload capability by default.
> > >
> >
> > Hi Ghalem,
> >
> > This patch enables announcement of the DEV_TX_OFFLOAD_MULTI_SEGS
> > capability, but still the application may not request this offload.
> >
> > As ENA PMD currently assumes all the mbufs may have multiple segments
> > (and we don't have fast-path for the other cases), I suggest
> > overwriting this flag in the ena_dev_configure(), similar to what
> > we're doing with the DEV_RX_OFFLOAD_RSS_HASH flag.
>
> To give some more context, our application currently checks if the
> driver supports multi-segments by checking its capabilities, and asks
> for the feature if it is advertised.
>
> When dealing with drivers that do not advertise this capability, our app
> linearizes the segmented mbufs before sending them to the driver.
>
> I think this is the proper way to use the API: if the driver supports to
> handle multisegmented mbufs, it should advertise the capability.
>
> Regards,
> Olivier
>

Hi Olivier,

I agree we should advertise it. However, after advertising this
option, the application should ask PMD to use this feature if I
understand the offload API correctly.
I was thinking about the PMD behavior if this option won't be
requested by the application - it would be the same as for the
multisegment setup, that's why I suggested to also override this
feature at the configuration step.

With the RSS hash feature we're doing exactly the same - first we're
advertising that it's available, and then (if RSS was enabled), we're
setting this offload as enabled, even though the application didn't
request it explicitly.

Anyway, I won't be holding push of this patch as we're close to rc3.
@Ghalem, please add the fixline and Cc the dpdk@stable.org in the
commit log, so we will have this commit backported.

Thanks,
Michal