Re: [PATCH v2] net/intel: deprecate some SSE paths

[Kevin Traynor <ktraynor@redhat.com>]

On 18/07/2025 17:13, Bruce Richardson wrote:
> On Fri, Jul 18, 2025 at 05:05:45PM +0100, Kevin Traynor wrote:
>> On 18/07/2025 16:19, Bruce Richardson wrote:
>>> On Fri, Jul 18, 2025 at 04:03:17PM +0100, Kevin Traynor wrote:
>>>> On 03/07/2025 15:31, Ciara Loftus wrote:
>>>>> The SSE rx and tx paths will be removed from the i40e, iavf and ice
>>>>> drivers in the 25.11 release. Each of these drivers have faster
>>>>> vector paths (AVX2 and AVX-512) which have feature parity with the
>>>>> soon to be removed SSE paths. In environments where AVX2 or AVX-512
>>>>> are not supported, the scalar path will still be used, which also has
>>>>> feature parity.
>>>>>
>>>>> Signed-off-by: Ciara Loftus <ciara.loftus@intel.com> ---
>>>>> doc/guides/rel_notes/deprecation.rst | 7 +++++++ 1 file changed, 7
>>>>> insertions(+)
>>>>>
>>>>> diff --git a/doc/guides/rel_notes/deprecation.rst
>>>>> b/doc/guides/rel_notes/deprecation.rst index e2d4125308..0d020c9c1f
>>>>> 100644 --- a/doc/guides/rel_notes/deprecation.rst +++
>>>>> b/doc/guides/rel_notes/deprecation.rst @@ -80,6 +80,13 @@ Deprecation
>>>>> Notices and the header struct ``rte_vxlan_gpe_hdr`` with the macro
>>>>> ``RTE_ETHER_VXLAN_GPE_HLEN`` will be removed in DPDK 25.11.
>>>>>  
>>>>> +* net/intel: drivers that have an SSE vector path alongside other
>>>>> vector paths, +  namely i40e, iavf and ice, will have their SSE
>>>>> vector paths removed in DPDK 25.11.  +  Modern x86 systems all
>>>>> support AVX2, if not AVX-512, so the SSE path is no longer +  widely
>>>>> used. This change will not result in any feature loss, as the
>>>>> fallback +  scalar paths which have feature parity with SSE will be
>>>>> used in the cases where +  the SSE paths would have been used.  + *
>>>>> ethdev: The flow API matching pattern structures, ``struct
>>>>> rte_flow_item_*``, should start with relevant protocol header
>>>>> structure from lib/net/.  The individual protocol header fields and
>>>>> the protocol header struct
>>>>
>>>> I'm not aware of anyone using hardware that old and relying on SSE,
>>>> but it seems a bit short notice for a patch to remove hardware
>>>> support.
>>>>
>>>> Would it hurt much to give it a longer deprecation so anyone who needs
>>>> to prepare by upgrade, or taking 25.11 with support etc. can do that ?
>>>>
>>> Do we think that will make a difference? After all, dropping the SSE
>>> path won't break DPDK on older hardware, it will only run a bit slower
>>> using the scalar path. Beyond that, it would only affect deployments
>>> with new/latest DPDK on old hardware - obviously old hardware running
>>> older DPDK would be unaffected.
>>>
>>
>> Don't disagree, and it does seem a bit of mismatch using old hw and new
>> DPDK, but I needed to spend a bit of time to try and check if this would
>> impact wrt systems used, compile options, product upgrade paths etc. so
>> others might be in same boat.
>>
>> Alternatively, could put the deprecation now and revisit if anyone
>> complains before 25.11.
>>
> Sure. Let's deprecate now and if there are any objections or we decide to
> postpone the removal in 25.11 that is fine.
> 

Sounds good.

Acked-by: Kevin Traynor <ktraynor@redhat.com>

> /Bruce
>