On 4/30/2020 8:07 PM, Tariq Toukan wrote:
On 4/30/2020 2:22 PM, Jesper Dangaard Brouer wrote:
The mlx5 driver have multiple memory models, which are also changed
according to whether a XDP bpf_prog is attached.
The 'rx_striding_rq' setting is adjusted via ethtool priv-flags e.g.:
# ethtool --set-priv-flags mlx5p2 rx_striding_rq off
On the general case with 4K page_size and regular MTU packet, then
the frame_sz is 2048 and 4096 when XDP is enabled, in both modes.
The info on the given frame size is stored differently depending on the
RQ-mode and encoded in a union in struct mlx5e_rq union wqe/mpwqe.
In rx striding mode rq->mpwqe.log_stride_sz is either 11 or 12, which
corresponds to 2048 or 4096 (MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ).
In non-striding mode (MLX5_WQ_TYPE_CYCLIC) the frag_stride is stored
in rq->wqe.info.arr[0].frag_stride, for the first fragment, which is
what the XDP case cares about.
To reduce effect on fast-path, this patch determine the frame_sz at
setup time, to avoid determining the memory model runtime. Variable
is named first_frame_sz to make it clear that this is only the frame
size of the first fragment.
This mlx5 driver does a DMA-sync on XDP_TX action, but grow is safe
as it have done a DMA-map on the entire PAGE_SIZE. The driver also
already does a XDP length check against sq->hw_mtu on the possible
XDP xmit paths mlx5e_xmit_xdp_frame() + mlx5e_xmit_xdp_frame_mpwqe().
V2: Fix that frag_size need to be recalc before creating SKB.
Cc: Tariq Toukan <tariqt@xxxxxxxxxxxx>
Cc: Saeed Mahameed <saeedm@xxxxxxxxxxxx>
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
---
drivers/net/ethernet/mellanox/mlx5/core/en.h | 1 +
drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 1 +
drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 6 ++++++
drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 2 ++
4 files changed, 10 insertions(+)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h
b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 23701c0e36ec..ba6a0ee297c6 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -652,6 +652,7 @@ struct mlx5e_rq {
struct {
u16 umem_headroom;
u16 headroom;
+ u32 first_frame_sz;
I also think that a better name would be: frame0_sz, or frag0_sz.
Thanks.
