> -----Original Message-----
> From: fengchengwen <[email protected]>
> Sent: Friday, May 6, 2022 2:36 PM
> To: Rahul Bhansali <[email protected]>; [email protected]; Ruifeng Wang
> <[email protected]>; Jan Viktorin <[email protected]>; Bruce
> Richardson <[email protected]>
> Cc: [email protected]
> Subject: Re: [EXT] Re: [PATCH 2/2] config/arm: disable SVE for cn10k
>
> On 2022/5/6 12:54, Rahul Bhansali wrote:
> >
> >
> >> -----Original Message-----
> >> From: fengchengwen <[email protected]>
> >> Sent: Friday, May 6, 2022 8:00 AM
> >> To: Rahul Bhansali <[email protected]>; [email protected]; Ruifeng
> >> Wang <[email protected]>; Jan Viktorin
> <[email protected]>;
> >> Bruce Richardson <[email protected]>
> >> Cc: Jerin Jacob Kollanukkaran <[email protected]>
> >> Subject: [EXT] Re: [PATCH 2/2] config/arm: disable SVE for cn10k
> >>
> >> External Email
> >>
> >> ---------------------------------------------------------------------
> >> - On 2022/5/5 22:27, Rahul Bhansali wrote:
> >>> This disable the SVE flag for cn10k.
> >>>
> >>> Performance impact:-
> >>> With l3fwd example, lpm lookup performance increased by ~21% if
> Neon
> >>> is used instead of SVE.
> >>>
> >>> Signed-off-by: Rahul Bhansali <[email protected]>
> >>> ---
> >>> config/arm/meson.build | 3 ++-
> >>> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> >>> dafb342cc6..39b7a1270c 100644
> >>> --- a/config/arm/meson.build
> >>> +++ b/config/arm/meson.build
> >>> @@ -281,7 +281,8 @@ soc_cn10k = {
> >>> ],
> >>> 'part_number': '0xd49',
> >>> 'extra_march_features': ['crypto'],
> >>> - 'numa': false
> >>> + 'numa': false,
> >>> + 'sve': false
> >>
> >> Suggest remove sve2 flag:
> >> '0xd49': {
> >> 'march': 'armv8.5-a',
> >> 'march_features': ['sve2'], ---remove 'sve2'
> >> 'flags': [
> >> ['RTE_MACHINE', '"neoverse-n2"'],
> >> ['RTE_ARM_FEATURE_ATOMICS', true],
> >> ['RTE_MAX_LCORE', 64],
> >> ['RTE_MAX_NUMA_NODES', 1]
> >> ]
> >> }
> >>
> > If I remove here, then this will also change for " Arm Neoverse N2 soc_n2",
> because part_number is same, Right ?
> > Because of this reason, I thought to have separate flag instead of updating
> march_features.
>
> This new add flag only impact hand-writen sve code, but auto-vectorization is
> also enabled when sve is enabled at march_features.
Agree.
> Maybe NEON-based automated vector code performs better than SVE-
> based.
>
> I think it's OK to add separate flag in soc_xxx struct, but suggest it also
> impact
> auto-vectorization.
I would suggest the flag to control only RTE_HAS_SVE_ACLE, i.e. hand written
code using SVE C language intrinsics.
For auto-vectorization, I think it is compilers duty to vectorize in the most
performant way, use whatever resource hardware provided.
>
> So for one soc which test or optimize well on sve, it could turn the flag to
> true.
>
> >
> >>> }
> >>>
> >>> soc_dpaa = {
> >>>
> >
