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

[Slava Ovsiienko]

> -----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