Re: [PATCH v2 5/8] net/mlx4: merge Tx queue rings management

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Wed, Dec 06, 2017 at 02:48:10PM +0000, Matan Azrad wrote:
> The Tx queue send ring was managed by Tx block head,tail,count and mask
> management variables which were used for managing the send queue remain
> space and next places of empty or completed work queue entries.
> 
> This method suffered from an actual addresses recalculation per packet,
> an unnecessary Tx block based calculations and an expensive dual
> management of Tx rings.
> 
> Move send queue ring calculation to be based on actual addresses while
> managing it by descriptors ring indexes.
> 
> Add new work queue entry pointer to the descriptor element to hold the
> appropriate entry in the send queue.
> 
> Signed-off-by: Matan Azrad <matan@mellanox.com>

A few more comments on this version below.

<snip>
> diff --git a/drivers/net/mlx4/mlx4_rxtx.c b/drivers/net/mlx4/mlx4_rxtx.c
> index adf02c0..2467d1d 100644
> --- a/drivers/net/mlx4/mlx4_rxtx.c
> +++ b/drivers/net/mlx4/mlx4_rxtx.c
> @@ -61,9 +61,6 @@
>  #include "mlx4_rxtx.h"
>  #include "mlx4_utils.h"
>  
> -#define WQE_ONE_DATA_SEG_SIZE \
> -	(sizeof(struct mlx4_wqe_ctrl_seg) + sizeof(struct mlx4_wqe_data_seg))
> -
>  /**
>   * Pointer-value pair structure used in tx_post_send for saving the first
>   * DWORD (32 byte) of a TXBB.
> @@ -268,52 +265,48 @@ struct pv {
>   *
>   * @param sq
>   *   Pointer to the SQ structure.
> - * @param index
> - *   Index of the freed WQE.
> - * @param num_txbbs
> - *   Number of blocks to stamp.
> - *   If < 0 the routine will use the size written in the WQ entry.
> - * @param owner
> - *   The value of the WQE owner bit to use in the stamp.
> + * @param wqe
> + *   Pointer of WQE address to stamp.

Clarification on what happens on return is primarily needed here actually:

 @param[in, out] wqe
   Pointer of WQE address to stamp. This value is modified on return to
   store the address of the next WQE.

>   *
>   * @return
> - *   The number of Tx basic blocs (TXBB) the WQE contained.
> + *   WQE size and updates WQE address to the next WQE.

You can leave the previous comment if @param wqe is properly documented.

<snip>
> @@ -654,7 +639,7 @@ struct pv {
>  
>  #ifndef NDEBUG
>  			/* Poisoning. */
> -			memset(elt, 0x66, sizeof(*elt));
> +			memset(elt->buf, 0x66, sizeof(struct rte_mbuf));

This likely causes a crash (did you test in debug mode?) the goal is to
poison the buffer address, not the entire mbuf. This should read:

 memset(&elt->buf, 0x66, sizeof(elt->buf));

-- 
Adrien Mazarguil
6WIND