[dpdk-dev] [PATCH v4 4/4] net/mlx5: enforce Tx num of segments limitation

Yongseok Koh yskoh at mellanox.com
Thu Sep 14 10:05:25 CEST 2017




Thanks!
Yongseok
> On Sep 13, 2017, at 10:23 PM, Shahaf Shuler <shahafs at mellanox.com> wrote:
> 
> Hi Yongseok,
> 
> Wednesday, September 13, 2017 10:52 PM, Yongseok Koh:
>>> 
>>> +/* Maximum number of DS in WQE. */
>>> +#define MLX5_MAX_DS 63
>> How about make it consistent with MLX5_MPW_DSEG_MAX by naming
>> MLX5_DSEG_MAX?
> 
> It doesn't have the same meaning. 
> 
> The MLX5_MPW_DSEG_MAX is to limit the number of mbuf segments (buf->nb_segs) for multi packet wqe.  The inline part  is taken into account differently. 
> The MLX_MAX_DS is to limit the number data segments (i.e. MLX5_WQE_DWORD_SIZE) that could be set into a WQE. This includes everything (inline, ctrl seg, eth seg, pointers).
> For the regular Tx burst there are many options for different inline sizes which impact on the max number of mbuf segments possible.
I should've been clearer. I just suggested a small change from DS to DSEG as I thought DS and DSEG are same. But if it just comes from the field name in WQE Ctrl segment, MLX5_WQE_DS_MAX or MLX5_WQE_CTRL_DS_MAX could be good. I hoped it could be a little more explanatory. I'm not good at naming, will defer to you. :-)

> BTW - am still not sure why we have the MLX5_MPW_DSEG_MAX limitation.
I don't know either. We should discuss it with chip design.

Thanks
Yongseok 


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