Re: [dpdk-dev] Please any one who can help me with librte_sched

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

Hi Ariel,

I think you put your finger precisely on the problem associated with your approach: you have to iterate through all the queues and free up the packets, which takes a lot of time. Obviously this is not done by the rte_sched API.

Maybe a limited workaround for this approach would be to create and service the parallel rte_sched using a different CPU core, while the previous CPU core takes its time to free up all the packets and data structures correctly.

Regards,
Cristian

From: Ariel Rodriguez [mailto:arodriguez@callistech.com]
Sent: Wednesday, May 28, 2014 1:46 AM
To: Dumitrescu, Cristian
Cc: Stephen Hemminger; dev@dpdk.org
Subject: Re: [dpdk-dev] Please any one who can help me with librte_sched

Thank you perfect explanation, i think im going to creating a new parallel rte_sched_port and change the reference with managment core updating the tx/sched core. So, what happens with the packets on the old reference if i just do rte_port_free on it, are them leaked? Is there a why to flush the rte_sched_port or maybe gets the packet total size somewhere?.
Anyway the rcu algoritm fits ok in this aproach ... but maybe there is a way to flush the old reference port, and work from there with the recently  created rte_sched_port ....

Regars,
Ariel.

On Tue, May 27, 2014 at 3:31 PM, Dumitrescu, Cristian <cristian.dumitrescu@intel.com<mailto:cristian.dumitrescu@intel.com>> wrote:
Hi Ariel,

What's wrong with calling rte_sched_subport_config() and rte_sched_pipe_config() during run-time?

This assumes that:

1. Port initialization is done, which includes the following:
a) the number of subports, pipes per subport are fixed
b) the queues are all created and their size is fixed
c) the pipe profiles are defined
d) Basically the maximal data structures get created (maximum number of supports, pipes and queues) with no run-time changes allowed, apart for the bandwidth related parameters. Queues that do not receive packets are not used now, they will be used as soon as they get packets. The packets-to-queues mapping logic can change over time, as well as the level of activity for different users/queues.

2. The CPU core calling the subport/pipe config functions is the same as the core doing enque/dequeue for this port (for thread safety reasons).
a) As you say, the management core can send update requests to the core running the scheduler, with the latter sampling the request queue regularly and performing the updates.

Regards,
Cristian


-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org<mailto:dev-bounces@dpdk.org>] On Behalf Of Stephen Hemminger
Sent: Tuesday, May 27, 2014 5:35 PM
To: Ariel Rodriguez
Cc: dev@dpdk.org<mailto:dev@dpdk.org>
Subject: Re: [dpdk-dev] Please any one who can help me with librte_sched

On Tue, 27 May 2014 10:33:02 -0300
Ariel Rodriguez <arodriguez@callistech.com<mailto:arodriguez@callistech.com>> wrote:

> Hello , this is my third mail , the previous mails have not been answered
> yet.
>
> I justo need someone explains to me  how the librte_sched framework behaves
> in a specific situation.
>
> I have a managment application , this connects with a ring with the tx
> core, when a user applies some configuration of the bandwith mangement ,
> the tx core read the message in the ring parse the configuration in a
> rte_port_params struct , subport_params and pipe_params, then creates a new
> rte_sched from scratch , and then changes the pointer of the current
> rte_sched_port currently doing scheduling and then the code execurte
> rte_sched_port_free() for the unreference (reference by temporal pointer)
> rte_sched_port . This is the only way i found for applying dinamic
> configuration or changes to the qos framework.
> So, with this, what happens with the packets attached to the old
> rte_sched_port while is deleted? are those lost packets inside the
> rte_sched_port generates memory leaks?  how can i recover this packets _
> just dequeing from the port scheduler? Where the port scheduler  indicates
> empty packets in the queu state?
>
> Is there a better way to achieve this kind of behaviour? i just need to
> update  the rte_sched_port configuration dinamically, and i want to change
> the current pipe configuration and sub port configuration also.
>
> Regards .

If you need to do dynamic changes, I would recommend using an RCU type
algorithm where you exchange in new parameters and then cleanup/free
after a grace period.  See http://lttng.org/urcu
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--------------------------------------------------------------
Intel Shannon Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
Business address: Dromore House, East Park, Shannon, Co. Clare

This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.