[dpdk-dev] [RFC] ethdev: support Tx queue free descriptor query

[Jerin Jacob]

On Thu, Jan 4, 2024 at 6:46 PM Dumitrescu, Cristian
<cristian.dumitrescu at intel.com> wrote:
>
>
>
> > -----Original Message-----
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> > <cristian.dumitrescu at intel.com>; Jerin Jacob <jerinj at marvell.com>
> > Subject: [dpdk-dev] [RFC] ethdev: support Tx queue free descriptor query
> >
> > From: Jerin Jacob <jerinj at marvell.com>
> >
> > Introduce a new API to retrieve the number of available free descriptors
> > in a Tx queue. Applications can leverage this API in the fast path to
> > inspect the Tx queue occupancy and take appropriate actions based on the
> > available free descriptors.
> >
> > A notable use case could be implementing Random Early Discard (RED)
> > in software based on Tx queue occupancy.
> >
> > Signed-off-by: Jerin Jacob <jerinj at marvell.com>
> > ---
> >  doc/guides/nics/features.rst         | 10 ++++
> >  doc/guides/nics/features/default.ini |  1 +
> >  lib/ethdev/ethdev_trace_points.c     |  3 ++
> >  lib/ethdev/rte_ethdev.h              | 78 ++++++++++++++++++++++++++++
> >  lib/ethdev/rte_ethdev_core.h         |  7 ++-
> >  lib/ethdev/rte_ethdev_trace_fp.h     |  8 +++
> >  6 files changed, 106 insertions(+), 1 deletion(-)
>
> Hi Jerin,

Hi Cristian,

>
> I think having an API to get the number of free descriptors per queue is a good idea. Why have it only for TX queues and not for RX queues as well?

I see no harm in adding for Rx as well. I think, it is better to have
separate API for each instead of adding argument as it is fast path
API.
If so, we could add a new API when there is any PMD implementation or
need for this.

>
> Regards,
> Cristian