Hi, Jiawei
> -----Original Message-----
> From: Jiawei Zhu <17826875...@163.com>
> Sent: Monday, March 22, 2021 17:46
> To: dev@dpdk.org
> Cc: zhujiawe...@huawei.com; Matan Azrad <ma...@nvidia.com>; Shahaf
> Shuler <shah...@nvidia.com>; Slava Ovsiienko <viachesl...@nvidia.com>
> Subject: [PATCH] net/mlx5: add Rx checksum offload flag return bad
>
> From: Jiawei Zhu <zhujiawe...@huawei.com>
>
> When open the rx checksum offload and receive the wrong checksum, add
> the ol_flags return bad. And it's not best to use multiplication and division
> here.
I'm sorry, there should be no any multiplications and divisions - the arguments
are constants (can be determined at compilation time) and ara power of 2,
hence compiler engages simple shifts. For example (I did rxq_cq_to_ol_flags not
inline to
get the listing for x86-64):
29 rxq_cq_to_ol_flags:
21 /*
22 * An architecture-optimized byte swap for a 16-bit
value.
23 *
24 * Do not use this function directly. The preferred
function is rte_bswap16().
25 */
26 static inline uint16_t rte_arch_bswap16(uint16_t _x)
27 {
28 uint16_t x = _x;
29 0034 86D6 asm volatile ("xchgb %b[x1],%h[x2]"
30 : [x1] "=Q" (x)
37
38 0036 89D0 movl %edx,%eax
39 0038 6681E200 andw $512,%dx
39 02
40 003d 66250004 andw $1024,%ax
41 0041 0FB7D2 movzwl %dx,%edx
42 0044 0FB7C0 movzwl %ax,%eax
43 0047 48C1EA02 shrq $2,%rdx
44 004b 48C1E802 shrq $2,%rax
45 004f 09D0 orl %edx,%eax
46 0051 C3 ret
As we can see - there is no any mul/div and no any branches, that
improves the performance.
>
> Signed-off-by: Jiawei Zhu <zhujiawe...@huawei.com>
> ---
> drivers/net/mlx5/mlx5_rxtx.c | 17 ++++++++++-------
> drivers/net/mlx5/mlx5_utils.h | 6 ------
> 2 files changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
> index e3ce9fd..9233af8 100644
> --- a/drivers/net/mlx5/mlx5_rxtx.c
> +++ b/drivers/net/mlx5/mlx5_rxtx.c
> @@ -1325,13 +1325,16 @@ enum mlx5_txcmp_code {
> uint32_t ol_flags = 0;
> uint16_t flags = rte_be_to_cpu_16(cqe->hdr_type_etc);
>
> - ol_flags =
> - TRANSPOSE(flags,
> - MLX5_CQE_RX_L3_HDR_VALID,
> - PKT_RX_IP_CKSUM_GOOD) |
> - TRANSPOSE(flags,
> - MLX5_CQE_RX_L4_HDR_VALID,
> - PKT_RX_L4_CKSUM_GOOD);
> + if (flags & MLX5_CQE_RX_L3_HDR_VALID)
> + ol_flags |= PKT_RX_IP_CKSUM_GOOD;
> + else
> + ol_flags |= PKT_RX_IP_CKSUM_BAD;
> +
If MLX5_CQE_RX_L3_HDR_VALID is not set - it does not always mean the sum is bad.
If might happen if HW just did not recognize the packet format (for example, for
some tunnels)
With best regards,
Slava
> + if (flags & MLX5_CQE_RX_L4_HDR_VALID)
> + ol_flags |= PKT_RX_IP_CKSUM_GOOD;
> + else
> + ol_flags |= PKT_RX_IP_CKSUM_BAD;
> +
> return ol_flags;
> }
>
> diff --git a/drivers/net/mlx5/mlx5_utils.h b/drivers/net/mlx5/mlx5_utils.h
> index 7a62187..2f71a23 100644
> --- a/drivers/net/mlx5/mlx5_utils.h
> +++ b/drivers/net/mlx5/mlx5_utils.h
> @@ -44,12 +44,6 @@
> #define NB_SEGS(m) ((m)->nb_segs)
> #define PORT(m) ((m)->port)
>
> -/* Transpose flags. Useful to convert IBV to DPDK flags. */ -#define
> TRANSPOSE(val, from, to) \
> - (((from) >= (to)) ? \
> - (((val) & (from)) / ((from) / (to))) : \
> - (((val) & (from)) * ((to) / (from))))
> -
> /*
> * For the case which data is linked with sequence increased index, the
> * array table will be more efficiect than hash table once need to serarch
> --
> 1.8.3.1
>
