[dpdk-dev] [PATCH / RFC] sched: Correct subport calcuation

[Dumitrescu, Cristian]

> -----Original Message-----
> From: Simon Kagstrom [mailto:simon.kagstrom at netinsight.net]
> Sent: Friday, June 10, 2016 7:29 AM
> To: Dumitrescu, Cristian <cristian.dumitrescu at intel.com>;
> stephen at networkplumber.org; dev at dpdk.org;
> thomas.monjalon at 6wind.com
> Subject: [PATCH / RFC] sched: Correct subport calcuation
> 
> Signed-off-by: Simon Kagstrom <simon.kagstrom at netinsight.net>
> ---
> I'm a total newbie to the rte_sched design and implementation, so I've
> added the RFC.
> 
> We get crashes (at other places in the scheduler) without this code.
> 
>  lib/librte_sched/rte_sched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/librte_sched/rte_sched.c b/lib/librte_sched/rte_sched.c
> index 1609ea8..b46ecfb 100644
> --- a/lib/librte_sched/rte_sched.c
> +++ b/lib/librte_sched/rte_sched.c
> @@ -1869,7 +1869,7 @@ grinder_next_pipe(struct rte_sched_port *port,
> uint32_t pos)
> 
>  	/* Install new pipe in the grinder */
>  	grinder->pindex = pipe_qindex >> 4;
> -	grinder->subport = port->subport + (grinder->pindex / port-
> >n_pipes_per_subport);
> +	grinder->subport = port->subport + (grinder->pindex / port-
> >n_subports_per_port);
>  	grinder->pipe = port->pipe + grinder->pindex;
>  	grinder->pipe_params = NULL; /* to be set after the pipe structure is
> prefetched */
>  	grinder->productive = 0;
> --
> 1.9.1

Hi Simon,

NACK.

Each port has an array of queues (size is port->n_queues_per_port), which are organized into equal size groups associated with pipes and subports:
- Each pipe is assigned the next group of RTE_SCHED_QUEUES_PER_PIPE (i.e. 16) queues in ascending order;
- Each subport is assigned the next group of port->n_pipes_per_subport pipes (congurable parameter).
The following is true:
	n_queues_per_port = RTE_SCHED_QUEUES_PER_PIPE * n_pipes_per_subport * n_subports_per_port

Given a queue index (pipe_qindex), the following are true:
- Pipe index: pindex = pipe_qindex >> 4;
- Subport index (let's call it sindex): sindex = pindex / n_pipes_per_subport, right?

I don't know why you get crashes in your application, but what I do know is that your proposed method to compute sindex is not correct :)

Regards,
Cristian