Hi Adrien
> -----Original Message-----
> From: Adrien Mazarguil [mailto:adrien.mazarg...@6wind.com]
> Sent: Monday, October 30, 2017 4:23 PM
> To: Matan Azrad <ma...@mellanox.com>
> Cc: dev@dpdk.org; Ophir Munk <ophi...@mellanox.com>
> Subject: Re: [PATCH v3 1/7] net/mlx4: remove error flows from Tx fast path
>
> On Mon, Oct 30, 2017 at 10:07:23AM +0000, Matan Azrad wrote:
> > Move unnecessary error flows to DEBUG mode.
> >
> > Signed-off-by: Matan Azrad <ma...@mellanox.com>
> > Acked-by: Adrien Mazarguil <adrien.mazarg...@6wind.com>
>
> I missed a couple of details while reviewing the original version, the first
> one
> being mlx4_post_send()'s return value is still documented as updating
> rte_errno in case of error, it's not the case anymore after this patch.
>
Good attention, Will be fixed in next version.
> Please see below for the other one:
>
> > ---
> > drivers/net/mlx4/mlx4_rxtx.c | 16 ++++++----------
> > 1 file changed, 6 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/mlx4/mlx4_rxtx.c
> > b/drivers/net/mlx4/mlx4_rxtx.c
> <snip>
> > /**
> > @@ -510,8 +508,6 @@ struct pv {
> > assert(max <= elts_n);
> > /* Always leave one free entry in the ring. */
> > --max;
> > - if (max == 0)
> > - return 0;
> > if (max > pkts_n)
> > max = pkts_n;
> > for (i = 0; (i != max); ++i) {
>
> While minor, this change has nothing to do with this patch, right?
>
Yes you right, maybe it can be merged in patch 4/7.
> I think it can slightly degrade an application performance as it removes the
> guarantee that subsequent code only needs to be run if there is at least one
> packet to process in case the TX ring is constantly full (SW faster than HW).
>
In case the TX ring is full, the loop condition should fail in the start and
then return with 0 because the packet counter is 0.(more 2 checks)
Since this case are less common (in my opinion) than at least 1 free space in
ring, we can prevent this unnecessary check for all these common cases.
Are you sure the 2 extra check important for performance in this empty case?
Doesn't the application will call us again?
> Can you remove it?
>
> --
> Adrien Mazarguil
> 6WIND
