[dpdk-dev] [PATCH] net/mlx5: add Rx checksum offload flag return bad
Jiawei Zhu
17826875952 at 163.com
Wed Mar 24 17:22:22 CET 2021
Hi,Slava
Thanks for your explain,the multiplications and divisions are in the
TRANSPOSE,not in the rte_be_to_cpu_16. So I think use if-else directly
could improves the performance. And the second point about the bad sum,I
agree with you.
With best regards,
Jiawei
On 2021/3/24 12:33 上午, Slava Ovsiienko wrote:
> Hi, Jiawei
>
>> -----Original Message-----
>> From: Jiawei Zhu <17826875952 at 163.com>
>> Sent: Monday, March 22, 2021 17:46
>> To: dev at dpdk.org
>> Cc: zhujiawei12 at huawei.com; Matan Azrad <matan at nvidia.com>; Shahaf
>> Shuler <shahafs at nvidia.com>; Slava Ovsiienko <viacheslavo at nvidia.com>
>> Subject: [PATCH] net/mlx5: add Rx checksum offload flag return bad
>>
>> From: Jiawei Zhu <zhujiawei12 at 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 <zhujiawei12 at 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
>>
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