diff mbox series

[net-next] net/mlx5e: TX, Utilize WQ fragments edge for multi-packet WQEs

Message ID 1742391746-118647-1-git-send-email-tariqt@nvidia.com (mailing list archive)
State New
Delegated to: Netdev Maintainers
Headers show
Series [net-next] net/mlx5e: TX, Utilize WQ fragments edge for multi-packet WQEs | expand

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netdev/series_format success Single patches do not need cover letters
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 6 maintainers not CCed: rrameshbabu@nvidia.com ast@kernel.org bpf@vger.kernel.org hawk@kernel.org john.fastabend@gmail.com daniel@iogearbox.net
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1 this patch: 1
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 94 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest fail net-next-2025-03-19--18-00 (tests: 896)

Commit Message

Tariq Toukan March 19, 2025, 1:42 p.m. UTC 
For simplicity reasons, the driver avoids crossing work queue fragment
boundaries within the same TX WQE (Work-Queue Element). Until today, as
the number of packets in a TX MPWQE (Multi-Packet WQE) descriptor is not
known in advance, the driver pre-prepared contiguous memory for the
largest possible WQE. For this, when getting too close to the fragment
edge, having no room for the largest WQE possible, the driver was
filling the fragment remainder with NOP descriptors, aligning the next
descriptor to the beginning of the next fragment.

Generating and handling these NOPs wastes resources, like: CPU cycles,
work-queue entries fetched to the device, and PCI bandwidth.

In this patch, we replace this NOPs filling mechanism in the TX MPWQE
flow. Instead, we utilize the remaining entries of the fragment with a
TX MPWQE. If this room turns out to be too small, we simply open an
additional descriptor starting at the beginning of the next fragment.

Performance benchmark:
uperf test, single server against 3 clients.
TCP multi-stream, bidir, traffic profile "2x350B read, 1400B write".
Bottleneck is in inbound PCI bandwidth (device POV).

+---------------+------------+------------+--------+
|               | Before     | After      |        |
+---------------+------------+------------+--------+
| BW            | 117.4 Gbps | 121.1 Gbps | +3.1%  |
+---------------+------------+------------+--------+
| tx_packets    | 15 M/sec   | 15.5 M/sec | +3.3%  |
+---------------+------------+------------+--------+
| tx_nops       | 3  M/sec   | 0          | -100%  |
+---------------+------------+------------+--------+

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en.h    |  1 +
 .../net/ethernet/mellanox/mlx5/core/en/txrx.h   | 17 +++++++++++++++--
 .../net/ethernet/mellanox/mlx5/core/en/xdp.c    |  3 ++-
 .../net/ethernet/mellanox/mlx5/core/en/xdp.h    |  6 +++---
 drivers/net/ethernet/mellanox/mlx5/core/en_tx.c |  7 ++++---
 5 files changed, 25 insertions(+), 9 deletions(-)


base-commit: 23c9ff659140f97d44bf6fb59f89526a168f2b86
diff mbox series

Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 8df185e2ef7f..32ed4963b8ad 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -398,6 +398,7 @@  struct mlx5e_tx_mpwqe {
 	struct mlx5e_tx_wqe *wqe;
 	u32 bytes_count;
 	u8 ds_count;
+	u8 ds_count_max;
 	u8 pkt_count;
 	u8 inline_on;
 };
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h b/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h
index 5ec468268d1a..e837c21d3d21 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/txrx.h
@@ -214,6 +214,19 @@  static inline u16 mlx5e_txqsq_get_next_pi(struct mlx5e_txqsq *sq, u16 size)
 	return pi;
 }
 
+static inline u16 mlx5e_txqsq_get_next_pi_anysize(struct mlx5e_txqsq *sq,
+						  u16 *size)
+{
+	struct mlx5_wq_cyc *wq = &sq->wq;
+	u16 pi, contig_wqebbs;
+
+	pi = mlx5_wq_cyc_ctr2ix(wq, sq->pc);
+	contig_wqebbs = mlx5_wq_cyc_get_contig_wqebbs(wq, pi);
+	*size = min_t(u16, contig_wqebbs, sq->max_sq_mpw_wqebbs);
+
+	return pi;
+}
+
 void mlx5e_txqsq_wake(struct mlx5e_txqsq *sq);
 
 static inline u16 mlx5e_shampo_get_cqe_header_index(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe)
@@ -358,9 +371,9 @@  mlx5e_tx_dma_unmap(struct device *pdev, struct mlx5e_sq_dma *dma)
 
 void mlx5e_tx_mpwqe_ensure_complete(struct mlx5e_txqsq *sq);
 
-static inline bool mlx5e_tx_mpwqe_is_full(struct mlx5e_tx_mpwqe *session, u8 max_sq_mpw_wqebbs)
+static inline bool mlx5e_tx_mpwqe_is_full(struct mlx5e_tx_mpwqe *session)
 {
-	return session->ds_count == max_sq_mpw_wqebbs * MLX5_SEND_WQEBB_NUM_DS;
+	return session->ds_count == session->ds_count_max;
 }
 
 static inline void mlx5e_rqwq_reset(struct mlx5e_rq *rq)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index 6f3094a479e1..f803e1c93590 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -390,6 +390,7 @@  static void mlx5e_xdp_mpwqe_session_start(struct mlx5e_xdpsq *sq)
 		.wqe = wqe,
 		.bytes_count = 0,
 		.ds_count = MLX5E_TX_WQE_EMPTY_DS_COUNT,
+		.ds_count_max = sq->max_sq_mpw_wqebbs * MLX5_SEND_WQEBB_NUM_DS,
 		.pkt_count = 0,
 		.inline_on = mlx5e_xdp_get_inline_state(sq, session->inline_on),
 	};
@@ -501,7 +502,7 @@  mlx5e_xmit_xdp_frame_mpwqe(struct mlx5e_xdpsq *sq, struct mlx5e_xmit_data *xdptx
 
 	mlx5e_xdp_mpwqe_add_dseg(sq, p, stats);
 
-	if (unlikely(mlx5e_xdp_mpwqe_is_full(session, sq->max_sq_mpw_wqebbs)))
+	if (unlikely(mlx5e_xdp_mpwqe_is_full(session)))
 		mlx5e_xdp_mpwqe_complete(sq);
 
 	stats->xmit++;
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
index e054db1e10f8..446e492c6bb8 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
@@ -182,13 +182,13 @@  static inline bool mlx5e_xdp_get_inline_state(struct mlx5e_xdpsq *sq, bool cur)
 	return cur;
 }
 
-static inline bool mlx5e_xdp_mpwqe_is_full(struct mlx5e_tx_mpwqe *session, u8 max_sq_mpw_wqebbs)
+static inline bool mlx5e_xdp_mpwqe_is_full(struct mlx5e_tx_mpwqe *session)
 {
 	if (session->inline_on)
 		return session->ds_count + MLX5E_XDP_INLINE_WQE_MAX_DS_CNT >
-		       max_sq_mpw_wqebbs * MLX5_SEND_WQEBB_NUM_DS;
+		       session->ds_count_max;
 
-	return mlx5e_tx_mpwqe_is_full(session, max_sq_mpw_wqebbs);
+	return mlx5e_tx_mpwqe_is_full(session);
 }
 
 struct mlx5e_xdp_wqe_info {
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index f8c7912abe0e..4fd853d19e31 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -525,9 +525,9 @@  static void mlx5e_tx_mpwqe_session_start(struct mlx5e_txqsq *sq,
 {
 	struct mlx5e_tx_mpwqe *session = &sq->mpwqe;
 	struct mlx5e_tx_wqe *wqe;
-	u16 pi;
+	u16 pi, num_wqebbs;
 
-	pi = mlx5e_txqsq_get_next_pi(sq, sq->max_sq_mpw_wqebbs);
+	pi = mlx5e_txqsq_get_next_pi_anysize(sq, &num_wqebbs);
 	wqe = MLX5E_TX_FETCH_WQE(sq, pi);
 	net_prefetchw(wqe->data);
 
@@ -535,6 +535,7 @@  static void mlx5e_tx_mpwqe_session_start(struct mlx5e_txqsq *sq,
 		.wqe = wqe,
 		.bytes_count = 0,
 		.ds_count = MLX5E_TX_WQE_EMPTY_DS_COUNT,
+		.ds_count_max = num_wqebbs * MLX5_SEND_WQEBB_NUM_DS,
 		.pkt_count = 0,
 		.inline_on = 0,
 	};
@@ -626,7 +627,7 @@  mlx5e_sq_xmit_mpwqe(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 	mlx5e_tx_mpwqe_add_dseg(sq, &txd);
 	mlx5e_tx_skb_update_hwts_flags(skb);
 
-	if (unlikely(mlx5e_tx_mpwqe_is_full(&sq->mpwqe, sq->max_sq_mpw_wqebbs))) {
+	if (unlikely(mlx5e_tx_mpwqe_is_full(&sq->mpwqe))) {
 		/* Might stop the queue and affect the retval of __netdev_tx_sent_queue. */
 		cseg = mlx5e_tx_mpwqe_session_complete(sq);