[PATCH net-next 06/15] net/mlx5e: reduce the max log mpwrq sz for ECPF and reps

Tariq Toukan
2025-02-09T10:19:35Z

From: William Tu <witu@nvidia.com>

For the ECPF and representors, reduce the max MPWRQ size from 256KB (18)
to 128KB (17). This prepares the later patch for saving representor
memory.

With Striding RQ, there is a minimum of 4 MPWQEs. So with 128KB of max
MPWRQ size, the minimal memory is 4 * 128KB = 512KB. When creating page
pool, consider 1500 mtu, the minimal page pool size will be 512KB/4KB =
128 pages = 256 rx ring entries (2 entries per page).

Before this patch, setting RX ringsize (ethtool -G rx) to 256 causes
driver to allocate page pool size more than it needs due to max MPWRQ
is 256KB (18). Ex: 4 * 256KB = 1MB, 1MB/4KB = 256 pages, but actually
128 pages is good enough. Reducing the max MPWRQ to 128KB fixes the
limitation.

Signed-off-by: William Tu <witu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 --
.../net/ethernet/mellanox/mlx5/core/en/params.c | 15 +++++++++++----
2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 979fc56205e1..534fdd27c8de 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -95,8 +95,6 @@ struct page_pool;
#define MLX5_MPWRQ_DEF_LOG_STRIDE_SZ(mdev) \
MLX5_MPWRQ_LOG_STRIDE_SZ(mdev, order_base_2(MLX5E_RX_MAX_HEAD))

-#define MLX5_MPWRQ_MAX_LOG_WQE_SZ 18
-
/* Keep in sync with mlx5e_mpwrq_log_wqe_sz.
* These are theoretical maximums, which can be further restricted by
* capabilities. These values are used for static resource allocations and
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
index 64b62ed17b07..e37d4c202bba 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -10,6 +10,9 @@
#include <net/page_pool/types.h>
#include <net/xdp_sock_drv.h>

+#define MLX5_MPWRQ_MAX_LOG_WQE_SZ 18
+#define MLX5_REP_MPWRQ_MAX_LOG_WQE_SZ 17
+
static u8 mlx5e_mpwrq_min_page_shift(struct mlx5_core_dev *mdev)
{
u8 min_page_shift = MLX5_CAP_GEN_2(mdev, log_min_mkey_entity_size);
@@ -103,18 +106,22 @@ u8 mlx5e_mpwrq_log_wqe_sz(struct mlx5_core_dev *mdev, u8 page_shift,
enum mlx5e_mpwrq_umr_mode umr_mode)
{
u8 umr_entry_size = mlx5e_mpwrq_umr_entry_size(umr_mode);
- u8 max_pages_per_wqe, max_log_mpwqe_size;
+ u8 max_pages_per_wqe, max_log_wqe_size_calc;
+ u8 max_log_wqe_size_cap;
u16 max_wqe_size;

/* Keep in sync with MLX5_MPWRQ_MAX_PAGES_PER_WQE. */
max_wqe_size = mlx5e_get_max_sq_aligned_wqebbs(mdev) * MLX5_SEND_WQE_BB;
max_pages_per_wqe = ALIGN_DOWN(max_wqe_size - sizeof(struct mlx5e_umr_wqe),
MLX5_UMR_FLEX_ALIGNMENT) / umr_entry_size;
- max_log_mpwqe_size = ilog2(max_pages_per_wqe) + page_shift;
+ max_log_wqe_size_calc = ilog2(max_pages_per_wqe) + page_shift;
+
+ WARN_ON_ONCE(max_log_wqe_size_calc < MLX5E_ORDER2_MAX_PACKET_MTU);

- WARN_ON_ONCE(max_log_mpwqe_size < MLX5E_ORDER2_MAX_PACKET_MTU);
+ max_log_wqe_size_cap = mlx5_core_is_ecpf(mdev) ?
+ MLX5_REP_MPWRQ_MAX_LOG_WQE_SZ : MLX5_MPWRQ_MAX_LOG_WQE_SZ;

- return min_t(u8, max_log_mpwqe_size, MLX5_MPWRQ_MAX_LOG_WQE_SZ);
+ return min_t(u8, max_log_wqe_size_calc, max_log_wqe_size_cap);
}

u8 mlx5e_mpwrq_pages_per_wqe(struct mlx5_core_dev *mdev, u8 page_shift,
--
2.45.0