[dpdk-dev] [PATCH v4 6/8] net/mlx5: introduce Tx burst routine template

[Ferruh Yigit]

On 7/22/2019 2:07 PM, Slava Ovsiienko wrote:
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yigit at intel.com>
>> Sent: Monday, July 22, 2019 14:53
>> To: Slava Ovsiienko <viacheslavo at mellanox.com>; dev at dpdk.org
>> Cc: Yongseok Koh <yskoh at mellanox.com>
>> Subject: Re: [dpdk-dev] [PATCH v4 6/8] net/mlx5: introduce Tx burst routine
>> template
>>
>> On 7/21/2019 3:24 PM, Viacheslav Ovsiienko wrote:
>>> Mellanox NICs support the wide set of Tx offloads. The supported
>>> offloads are reported by the mlx5 PMD in rte_eth_dev_info
>>> tx_offload_capa field. An application may choose any combination of
>>> supported offloads and configure the device appropriately. Some of Tx
>>> offloads may be not requested by application, or ever all of them may be
>> omitted.
>>> Most of the Tx offloads require some code branches in tx_burst routine
>>> to support ones. If Tx offload is not requested the tx_burst routine
>>> code may be significantly simplified and consume less CPU cycles.
>>>
>>> For example, if application does not engage TSO offload this code can
>>> be omitted, if multi-segment packet is not supposed the tx_burst may
>>> assume single mbuf packets only, etc.
>>>
>>> Currently, the mlx5 PMD implements multiple tx_burst subroutines for
>>> most common combinations of requested Tx offloads, each branch has its
>>> own dedicated implementation. It is not very easy to update, support
>>> and develop such kind of code - multiple branches impose the multiple
>>> points to process. Also many of frequently requested offload
>>> combinations are not supported yet. That leads to selecting of not
>>> completely matching tx_burst routine and harms the performance.
>>>
>>> This patch introduces the new approach for tx_burst code. It is
>>> proposed to develop the unified template for tx_burst routine, which
>>> supports all the Tx offloads and takes the compile time defined
>>> parameter describing the supposed set of supported offloads. On the
>>> base of this template, the compiler is able to generate multiple
>>> tx_burst routines highly optimized for the statically specified set of Tx
>> offloads.
>>> Next, in runtime, at Tx queue configuration the best matching
>>> optimized implementation of tx_burst is chosen.
>>>
>>> This patch intentionally omits the template internal implementation,
>>> but just introduces the template itself to emboss the approach of the
>>> multiple specially tuned tx_burst routines.
>>>
>>> Signed-off-by: Viacheslav Ovsiienko <viacheslavo at mellanox.com>
>>
>> Getting following build error with icc, can you please check?
>>
>>
>> .../dpdk/drivers/net/mlx5/mlx5_rxtx.c(4649): error #191: type qualifier is
>> meaningless on cast type
>>
>>
>>   MLX5_TXOFF_DECL(full_empw,
>>
> Sorry, I have no icc at my disposal now. What I can say (sorry again, it is obvious) 
> - It definitely does not like the MLX5_TXOFF_DECL macro. Most likely - "restrict" qualifier, I think.
> 
> With best regards, Slava
> 

Hi Slava,

I was hoping error log can give enough hint, but I tested by removing the
'restrict' keyword and it fixed the icc warning.

Can you please check if the 'icc' is right and 'restrict' is meaningless, if so
can you please send a patch to remove it?
else please let me know and I can make a patch to disable the specific icc warning.