Hi, Ruifeng
> -----Original Message-----
> From: Ruifeng Wang <ruifeng.w...@arm.com>
> Sent: Tuesday, June 1, 2021 11:31
> To: Raslan Darawsheh <rasl...@nvidia.com>; Matan Azrad
> <ma...@nvidia.com>; Shahaf Shuler <shah...@nvidia.com>; Slava Ovsiienko
> <viachesl...@nvidia.com>
> Cc: dev@dpdk.org; jer...@marvell.com; n...@arm.com;
> honnappa.nagaraha...@arm.com; Ruifeng Wang <ruifeng.w...@arm.com>;
> sta...@dpdk.org
> Subject: [PATCH 1/2] net/mlx5: remove redundant operations
>
> Some operations on mask are redundant and can be removed.
> The change yielded 1.6% performance gain on N1SDP.
> On ThunderX2, slight performance uplift was also observed.
>
> Fixes: 570acdb1da8a ("net/mlx5: add vectorized Rx/Tx burst for ARM")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Ruifeng Wang <ruifeng.w...@arm.com>
> ---
> drivers/net/mlx5/mlx5_rxtx_vec_neon.h | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
> b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
> index 2234fbe6b2..98a75b09c6 100644
> --- a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
> +++ b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
> @@ -768,18 +768,11 @@ rxq_cq_process_v(struct mlx5_rxq_data *rxq,
> volatile struct mlx5_cqe *cq,
> comp_mask), 0)) /
> (sizeof(uint16_t) * 8);
> /* D.6 mask out entries after the compressed CQE. */
> - mask = vcreate_u16(comp_idx <
> MLX5_VPMD_DESCS_PER_LOOP ?
> - -1UL >> (comp_idx * sizeof(uint16_t) * 8) :
> - 0);
> - invalid_mask = vorr_u16(invalid_mask, mask);
> + invalid_mask = vorr_u16(invalid_mask, comp_mask);
Mmmm... I'm not sure we can drop the masking compressed (and following) CQE
skip.
Let's consider the completion scenario (the series of 4 CQEs, each element is
64B long)
0: normal uncompressed CQE, ownership OK, format uncompressed, opcode OK, no
error
1: compressed CQE, ownership OK, format compressed, opcode OK, no error
2: miniCQE array, format can be any!!, may be discovered as ownership OK,
format uncompressed, opcode OK, no error
3: miniCQE array, format can be any!!, may be discovered as ownership OK,
format uncompressed, opcode OK, no error
Obviously, we should unconditionally mask out 2 and 3, regardless of recognized
their formats/opcode/error/etc.
I think we can get the diff above and skip diff below:
> /* D.7 count non-compressed valid CQEs. */
> n = __builtin_clzl(vget_lane_u64(vreinterpret_u64_u16(
> invalid_mask), 0)) / (sizeof(uint16_t) * 8);
> nocmp_n += n;
> - /* D.2 get the final invalid mask. */
> - mask = vcreate_u16(n < MLX5_VPMD_DESCS_PER_LOOP ?
> - -1UL >> (n * sizeof(uint16_t) * 8) : 0);
> - invalid_mask = vorr_u16(invalid_mask, mask);
and get the correct final invalid_mask - all compressed and invalid CQEs and
following ones will be masked out.
With best regards,
Slava
