-----Original Message-----
From: Slava Ovsiienko <redacted>
Sent: Friday, July 2, 2021 4:13 PM
To: Ruifeng Wang <redacted>; Raslan Darawsheh
[off-list ref]; Matan Azrad [off-list ref]; Shahaf Shuler
[off-list ref]
Cc: dev@dpdk.org; jerinj@marvell.com; nd <redacted>; Honnappa
Nagarahalli [off-list ref]; stable@dpdk.org
Subject: RE: [PATCH 1/2] net/mlx5: remove redundant operations

Hi, Ruifeng

Hi, Slava

quoted

-----Original Message-----
From: Ruifeng Wang <redacted>
Sent: Tuesday, June 1, 2021 11:31
To: Raslan Darawsheh <redacted>; Matan Azrad
[off-list ref]; Shahaf Shuler [off-list ref]; Slava
Ovsiienko [off-list ref]
Cc: dev@dpdk.org; jerinj@marvell.com; nd@arm.com;
honnappa.nagarahalli@arm.com; Ruifeng Wang [off-list ref];
stable@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: stable@dpdk.org

Signed-off-by: Ruifeng Wang <redacted>
---
 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

Thanks for your review and explanation about CQE processing details.
I did the change based on the fact that some calculations doesn't change the data. 
So some intermediate calculations were removed.

In the above diff section, result of 'mask' always equals to the nearest 'comp_mask' that above it.
So I just remoed 'mask' and use 'comp_mask' instead.

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:

quoted

 		/* 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.

This diff section is similar to the previous one.
'mask' always equals to the nearest 'invalid_mask' that above it.
So entire line "invalid_mask = vorr_u16(invalid_mask, mask);" can be removed.

Code logic is not changed. But I'm not sure the code change impacts readability
or maintainability that you may concern.

Thanks.

With best regards,
Slava