Re: [dpdk-dev] [patch v4] doc: announce API change in ethdev offload flags

[Jerin Jacob Kollanukkaran <jerinj@marvell.com>]

> -----Original Message-----
> From: Tom Barbette <barbette@kth.se>
> Sent: Friday, August 9, 2019 2:44 PM
> To: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>; Jerin Jacob
> Kollanukkaran <jerinj@marvell.com>; stephen@networkplumber.org;
> arybchenko@solarflare.com; hemant.agrawal@nxp.com;
> thomas@monjalon.net; ferruh.yigit@intel.com;
> bruce.richardson@intel.com; Neil Horman <nhorman@tuxdriver.com>; John
> McNamara <john.mcnamara@intel.com>; Marko Kovacevic
> <marko.kovacevic@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [patch v4] doc: announce API change in ethdev
> offload flags
> 
> I think the silent breaking is still not solved for DEV_RX_OFFLOAD_RSS_HASH
> and DEV_RX_OFFLOAD_FLOW_MARK.

Unlike ptype, presence of  rss hash and flow_mark will be marked in ol_flags
as PKT_RX_RSS_HASH  and PKT_RX_FDIR_ID. So NO application contract breakage.

> 
> An old application will still compile without any problem, but the RSS hash will
> not be written and the app will break... They should be negative. Eg
> DEV_RX_OFFLOAD_NO_RSS_HASH and
> DEV_RX_OFFLOAD_NO_FLOW_MARK?
> 
> Then, regarding the idea, are we sure it's better to add a configuration
> check/a branch than always copying a few bytes from a warm cache line to a
> warm cache line? Or some HW could free some internal resources? But
> drivers are free to ignore it so it is not a problem as opposed to silent
> breaking.
> 
> Tom
> 
> On 2019-08-09 10:17, pbhagavatula@marvell.com wrote:
> > From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> >
> > Add new offload flags ``DEV_RX_OFFLOAD_RSS`` and
> ``DEV_RX_OFFLOAD_FLOW_MARK``.
> > Add new function ``rte_eth_dev_set_supported_ptypes`` to allow
> application to
> > set specific ptypes to be updated in ``rte_mbuf::packet_type``
> >
> > Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> > Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
> > Acked-by: Jerin Jacob <jerinj@marvell.com>
> > Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
> > ---
> >   doc/guides/rel_notes/deprecation.rst | 23 +++++++++++++++++++++++
> >   1 file changed, 23 insertions(+)
> >
> > diff --git a/doc/guides/rel_notes/deprecation.rst
> b/doc/guides/rel_notes/deprecation.rst
> > index 37b8592b6..e4e2a85d7 100644
> > --- a/doc/guides/rel_notes/deprecation.rst
> > +++ b/doc/guides/rel_notes/deprecation.rst
> > @@ -78,3 +78,26 @@ Deprecation Notices
> >     to set new power environment if power environment was already
> initialized.
> >     In this case the function will return -1 unless the environment is unset
> first
> >     (using ``rte_power_unset_env``). Other function usage scenarios will not
> change.
> > +
> > +* ethdev: New offload flags ``DEV_RX_OFFLOAD_RSS_HASH`` and
> ``DEV_RX_OFFLOAD_FLOW_MARK``
> > +  will be added in 19.11.
> > +  This will allow application to enable or disable PMDs from updating
> > +  ``rte_mbuf::hash::rss`` and ``rte_mbuf::hash::fdir`` respectively.
> > +  This scheme will allow PMDs to avoid writes to ``rte_mbuf`` fields on Rx
> and
> > +  thereby improve Rx performance if application wishes do so.
> > +  In 19.11 PMDs will still update the fields even when the offloads are not
> > +  enabled.
> > +
> > +* ethdev: New function ``rte_eth_dev_set_supported_ptypes`` will be
> added in
> > +  19.11.
> > +  This will allow application to request PMD to set specific ptypes defined
> > +  through ``rte_eth_dev_set_supported_ptypes`` in
> ``rte_mbuf::packet_type``.
> > +  If application doesn't want any ptype information it can call
> > +  ``rte_eth_dev_set_supported_ptypes(ethdev_id,
> RTE_PTYPE_UNKNOWN)``
> > +  If application doesn't call ``rte_eth_dev_set_supported_ptypes`` PMD
> can
> > +  return ``rte_mbuf::packet_type`` with
> ``rte_eth_dev_get_supported_ptypes``.
> > +  If application is interested only in L2/L3 layer, it can inform the PMD to
> update
> > + ``rte_mbuf::packet_type`` with L2/L3 ptype by calling
> > + ``rte_eth_dev_set_supported_ptypes(ethdev_id, RTE_PTYPE_L2_MASK
> | RTE_PTYPE_L3_MASK)``.
> > +  This scheme will allow PMDs to avoid writes to ``rte_mbuf`` fields on Rx
> and
> > +  thereby improve Rx performance if application wishes do so.
> > --
> > 2.17.1
> >