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

[Bruce Richardson <bruce.richardson@intel.com>]

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.

/Bruce