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UCC polling frequency in case of scheduler

Question asked by Nicolas L'Hostis on Dec 22, 2015
Latest reply on Jan 12, 2016 by alexander.yakovlev

Hi,

 

I have a timing reponse difference when configuring UCCs with or without sheduler on a MPC8321E.

 

On one HW, I configure in ethernet

- UCC2 with 5 queues (QOS) + scheduler enabled

- UCC3 + UCC4 with 1 queue (no scheduler)

- UTPT register configured with 256

 

On the other HW, I configure in ethernet

- UCC2 + UCC3 with 5 queues (QOS) + scheduler enabled

- UCC4 with 1 queue (no scheduler)

- UTPT register configured with 256

 

On both configurations, the QUICC engine has the priority on the internal BUS.

 

When I perform a simple memory test to know my throughput, with no ethernet messages in RX nor TX, I notice that

- the first configuration is worse, which means to me that the UCC polls more.

 

If I activate the scheduler on all queues, I have exactly the same timing performances

Same timing performances also if I set the UTPT register to 384 only on the UCCs with 1 queue.

 

Has the scheduler a lower polling frequency compared to "no scheduler" ? If yes, any factor ?

Is it forbidden to enable a scheduler on a UCC with only one queue ? (it is specified in the doc §29.5.3.3: "When the number of send queues is 1 the scheduler shall be disabled.")

 

Thanks,

Nicolas L'HOSTIS

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