[dpdk-dev] [patch v4] doc: announce API change in ethdev offload flags
Andrew Rybchenko
arybchenko at solarflare.com
Fri Aug 9 11:22:30 CEST 2019
On 8/9/19 12:13 PM, Tom Barbette wrote:
> I think the silent breaking is still not solved for
> DEV_RX_OFFLOAD_RSS_HASH and DEV_RX_OFFLOAD_FLOW_MARK.
>
> 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.
It could be not delivered from NIC to host saving PCIe bandwidth. E.g.
flow mark plus RSS hash is 8 byte and it is more than 10% for small packet.
> Tom
>
> On 2019-08-09 10:17, pbhagavatula at marvell.com wrote:
>> From: Pavan Nikhilesh <pbhagavatula at 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 at marvell.com>
>> Acked-by: Andrew Rybchenko <arybchenko at solarflare.com>
>> Acked-by: Jerin Jacob <jerinj at marvell.com>
>> Acked-by: Hemant Agrawal <hemant.agrawal at 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
>>
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