Re: [dpdk-dev] [PATCH 20.11 00/12] add max SIMD bitwidth to EAL

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

Hi Ciara,
	I have not reviewed other patches in this series yet. Few questions inline.

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Ciara Power
> Sent: Friday, August 7, 2020 10:59 AM
> To: dev@dpdk.org
> Cc: bruce.richardson@intel.com; Ciara Power <ciara.power@intel.com>
> Subject: [dpdk-dev] [PATCH 20.11 00/12] add max SIMD bitwidth to EAL
> 
> A number of components in DPDK have optional AVX-512 or other vector code
> paths which can be selected at runtime. Rather than having each component
> provide its own mechanism to select a code path, this patchset adds support
> for a single setting to control what code paths are used.
Do you mean that all the components will have to use AVX-512?
IMO, different libraries might behave differently to the use of different vector sizes. Are we taking away the ability to use different vector sizes for different components.

> This can be used to enable some non-default code paths e.g. ones using AVX-
> 512, but also to limit the code paths to certain vector widths, or to scalar
> code only, which is useful for testing.
> 
> The max SIMD bitwidth setting can be set by the app itself through use of the
> available API, or can be overriden by a commandline argument passed by the
> user.
Arm platforms support SVE (scalable vector extensions) feature. With this feature, the code is agnostic to the vector size. i.e. same code can run on various vector sizes. There is no code yet in DPDK with this feature. But, it will be added in the near future. It would be good to handle this now so that we do not have issues in the future..

> 
> Ciara Power (12):
>   eal: add max SIMD bitwidth
>   eal: add default SIMD bitwidth values
>   net/i40e: add checks for max SIMD bitwidth
>   net/axgbe: add checks for max SIMD bitwidth
>   net/bnxt: add checks for max SIMD bitwidth
>   net/enic: add checks for max SIMD bitwidth
>   net/fm10k: add checks for max SIMD bitwidth
>   net/iavf: add checks for max SIMD bitwidth
>   net/ice: add checks for max SIMD bitwidth
>   net/ixgbe: add checks for max SIMD bitwidth
>   net/mlx5: add checks for max SIMD bitwidth
>   net/virtio: add checks for max SIMD bitwidth
> 
>  drivers/net/axgbe/axgbe_rxtx.c             |  3 +-
>  drivers/net/bnxt/bnxt_ethdev.c             |  6 ++-
>  drivers/net/enic/enic_rxtx_vec_avx2.c      |  3 +-
>  drivers/net/fm10k/fm10k_ethdev.c           | 11 ++--
>  drivers/net/i40e/i40e_rxtx.c               | 19 ++++---
>  drivers/net/iavf/iavf_rxtx.c               | 16 +++---
>  drivers/net/ice/ice_rxtx.c                 | 20 ++++---
>  drivers/net/ixgbe/ixgbe_rxtx.c             |  7 ++-
>  drivers/net/mlx5/mlx5_ethdev.c             |  3 +-
>  drivers/net/virtio/virtio_ethdev.c         | 12 +++--
>  lib/librte_eal/arm/include/rte_vect.h      |  2 +
>  lib/librte_eal/common/eal_common_options.c | 63
> ++++++++++++++++++++++
>  lib/librte_eal/common/eal_internal_cfg.h   |  8 +++
>  lib/librte_eal/common/eal_options.h        |  2 +
>  lib/librte_eal/include/generic/rte_vect.h  |  2 +
>  lib/librte_eal/include/rte_eal.h           | 31 +++++++++++
>  lib/librte_eal/ppc/include/rte_vect.h      |  2 +
>  lib/librte_eal/rte_eal_version.map         |  4 ++
>  lib/librte_eal/x86/include/rte_vect.h      |  2 +
>  19 files changed, 184 insertions(+), 32 deletions(-)
> 
> --
> 2.17.1