Re: [dpdk-dev] [PATCH] net/mlx5: fix Rx descriptor status returned value

[Didier Pallard <didier.pallard@6wind.com>]

well, please do if you don't mind,
You will validate it quicker, and I'm currently working on a
different topic.
Btw, do you think it's possible to have an implementation of
[r,t]x_status_descriptor functions for vectorized implementation?
thanks
didier

On Tue, Mar 17, 2020 at 9:33 AM Slava Ovsiienko <viacheslavo@mellanox.com>
wrote:

> >> From: Didier Pallard <didier.pallard@6wind.com>
> >> Sent: Monday, March 16, 2020 19:24
> >> To: Slava Ovsiienko <viacheslavo@mellanox.com>
> >> Cc: dev@dpdk.org; stable@dpdk.org; Matan Azrad <matan@mellanox.com>
> >> Subject: Re: [dpdk-dev] [PATCH] net/mlx5: fix Rx descriptor status
> returned value
> >> Well, you're right, another way to fix the problem could be to set up
> the queue size assuming the provided number
> >> is a number of packets in queue rather than a number of mbufs in queue.
>
> Yes, it is intended in queue setup routine. But, for mlx5 we have a bug
> for regular mlx5_rx_burst if scattering is enabled,
> the Rx queue is created with size wqe_n elements, should be wqe_n <<
> sges_n instead, to be able to receive the requested
> number of packets (wqe_n). I think we must fix. Would you like to update
> your patch, or should I provide mine?
>
> >> But not sure it's better, it's also important for the application/user
> to know the number of mbufs that could fit in a rx/tx queue,
> >> whatever the number of packets that it covers, since it is very
> important to size the memory pools correctly to avoid any
> >> mbuf shortage during system life.
> >> Thanks
> >> Didier
> To estimate - the number of "DPDK descriptors" should be multiplied by the
> maximal length of scattered packet chain.
>
> With best regards, Slava
>
> > -----Original Message-----
> > From: dev <mailto:dev-bounces@dpdk.org> On Behalf Of Didier Pallard
> > Sent: Friday, March 13, 2020 11:57
> > To: mailto:dev@dpdk.org
> > Cc: mailto:stable@dpdk.org
> > Subject: [dpdk-dev] [PATCH] net/mlx5: fix Rx descriptor status returned
> value
> >
> > Two bugs in rx_queue_count function:
> > - One entry may contain several segments, so 'used' must be multiplied
> >   by number of segments per entry to properly reflect the queue usage.
> > - rx_queue_count returns the number of entries used in queue, so it
> ranges
> >   from 0 to max number of entries in queue, not this number minus
> >   one.
> >
> > Fixes: 8788fec1f269 ("net/mlx5: implement descriptor status API")
> > Cc: mailto:stable@dpdk.org
> > Signed-off-by: Didier Pallard <mailto:didier.pallard@6wind.com>
> > ---
> >  drivers/net/mlx5/mlx5_rxtx.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
> index
> > 5ac63da8039d..17f80c25443e 100644
> > --- a/drivers/net/mlx5/mlx5_rxtx.c
> > +++ b/drivers/net/mlx5/mlx5_rxtx.c
> > @@ -500,7 +500,7 @@ rx_queue_count(struct mlx5_rxq_data *rxq)
> >               used += n;
> >               cqe = &(*rxq->cqes)[cq_ci & cqe_cnt];
> >       }
> > -     used = RTE_MIN(used, (1U << rxq->elts_n) - 1);
> > +     used = RTE_MIN(used * (1 << rxq->sges_n), 1U << rxq->elts_n);
> >       return used;
> >  }
> >
> > --
> > 2.24.1
>