From: Alexander Kozyrev <akozyrev@mellanox.com>
Date: Wed, 22 Jul 2020 20:32:38 +0000 (+0000)
Subject: net/mlx5: fix vectorized mini-CQE prefetching
X-Git-Url: http://git.droids-corp.org/?p=dpdk.git;a=commitdiff_plain;h=6f52bd338374e4bd54ff1f872928e53ebdf1108d

net/mlx5: fix vectorized mini-CQE prefetching

There was an optimization work to prefetch all the CQEs before
their invalidation. It allowed us to speed up the mini-CQE
decompression process by preheating the cache in the vectorized
Rx routine.

Prefetching of the next mini-CQE, on the other hand, showed
no difference in the performance on x86 platform. So, that was
removed. Unfortunately this caused the performance drop on ARM.

Prefetch the mini-CQE as well as all the soon to be
invalidated CQEs to get both CQE and mini-CQE on the hot path.

Fixes: 28a4b96321a3 ("net/mlx5: prefetch CQEs for a faster decompression")
Cc: stable@dpdk.org

Signed-off-by: Alexander Kozyrev <akozyrev@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
---

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_altivec.h b/drivers/net/mlx5/mlx5_rxtx_vec_altivec.h
index f5414eebad..cb4ce1a099 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec_altivec.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_altivec.h
@@ -158,7 +158,6 @@ rxq_cq_decompress_v(struct mlx5_rxq_data *rxq, volatile struct mlx5_cqe *cq,
 		for (i = 0; i < MLX5_VPMD_DESCS_PER_LOOP; ++i)
 			if (likely(pos + i < mcqe_n))
 				rte_prefetch0((void *)(cq + pos + i));
-
 		/* A.1 load mCQEs into a 128bit register. */
 		mcqe1 = (vector unsigned char)vec_vsx_ld(0,
 			(signed int const *)&mcq[pos % 8]);
@@ -287,6 +286,8 @@ rxq_cq_decompress_v(struct mlx5_rxq_data *rxq, volatile struct mlx5_cqe *cq,
 		pos += MLX5_VPMD_DESCS_PER_LOOP;
 		/* Move to next CQE and invalidate consumed CQEs. */
 		if (!(pos & 0x7) && pos < mcqe_n) {
+			if (pos + 8 < mcqe_n)
+				rte_prefetch0((void *)(cq + pos + 8));
 			mcq = (void *)&(cq + pos)->pkt_info;
 			for (i = 0; i < 8; ++i)
 				cq[inv++].op_own = MLX5_CQE_INVALIDATE;
diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
index 555c342626..6c3149523e 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
@@ -145,6 +145,7 @@ rxq_cq_decompress_v(struct mlx5_rxq_data *rxq, volatile struct mlx5_cqe *cq,
 				    -1UL << ((mcqe_n - pos) *
 					     sizeof(uint16_t) * 8) : 0);
 #endif
+
 		for (i = 0; i < MLX5_VPMD_DESCS_PER_LOOP; ++i)
 			if (likely(pos + i < mcqe_n))
 				rte_prefetch0((void *)(cq + pos + i));
@@ -227,6 +228,8 @@ rxq_cq_decompress_v(struct mlx5_rxq_data *rxq, volatile struct mlx5_cqe *cq,
 		pos += MLX5_VPMD_DESCS_PER_LOOP;
 		/* Move to next CQE and invalidate consumed CQEs. */
 		if (!(pos & 0x7) && pos < mcqe_n) {
+			if (pos + 8 < mcqe_n)
+				rte_prefetch0((void *)(cq + pos + 8));
 			mcq = (void *)&(cq + pos)->pkt_info;
 			for (i = 0; i < 8; ++i)
 				cq[inv++].op_own = MLX5_CQE_INVALIDATE;
diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
index 34e3397115..554924d7fc 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
@@ -135,7 +135,6 @@ rxq_cq_decompress_v(struct mlx5_rxq_data *rxq, volatile struct mlx5_cqe *cq,
 		for (i = 0; i < MLX5_VPMD_DESCS_PER_LOOP; ++i)
 			if (likely(pos + i < mcqe_n))
 				rte_prefetch0((void *)(cq + pos + i));
-
 		/* A.1 load mCQEs into a 128bit register. */
 		mcqe1 = _mm_loadu_si128((__m128i *)&mcq[pos % 8]);
 		mcqe2 = _mm_loadu_si128((__m128i *)&mcq[pos % 8 + 2]);
@@ -214,6 +213,8 @@ rxq_cq_decompress_v(struct mlx5_rxq_data *rxq, volatile struct mlx5_cqe *cq,
 		pos += MLX5_VPMD_DESCS_PER_LOOP;
 		/* Move to next CQE and invalidate consumed CQEs. */
 		if (!(pos & 0x7) && pos < mcqe_n) {
+			if (pos + 8 < mcqe_n)
+				rte_prefetch0((void *)(cq + pos + 8));
 			mcq = (void *)(cq + pos);
 			for (i = 0; i < 8; ++i)
 				cq[inv++].op_own = MLX5_CQE_INVALIDATE;