Re: [dpdk-dev] [PATCH 1/2] net/mlx5: remove redundant operations
From: Slava Ovsiienko <hidden>
Date: 2021-07-02 08:12:42
Hi, Ruifeng
quoted hunk ↗ jump to hunk
-----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.hb/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