[dpdk-users] Run-to-completion or Pipe-line for QAT PMD in DPDK

Trahe, Fiona fiona.trahe at intel.com
Mon Jan 21 19:52:02 CET 2019



> -----Original Message-----
> From: Changchun Zhang [mailto:changchun.zhang at oracle.com]
> Sent: Friday, January 18, 2019 6:53 PM
> To: Trahe, Fiona <fiona.trahe at intel.com>; Pathak, Pravin <pravin.pathak at intel.com>;
> users at dpdk.org
> Subject: RE: [dpdk-users] Run-to-completion or Pipe-line for QAT PMD in DPDK
> 
> HI Fiona,
> 
> Thanks!
> Changchun (Alex)
> 
> 
> -----Original Message-----
> From: Trahe, Fiona [mailto:fiona.trahe at intel.com]
> Sent: Friday, January 18, 2019 1:21 PM
> To: Changchun Zhang <changchun.zhang at oracle.com>; Pathak, Pravin <pravin.pathak at intel.com>;
> users at dpdk.org
> Cc: Trahe, Fiona <fiona.trahe at intel.com>
> Subject: RE: [dpdk-users] Run-to-completion or Pipe-line for QAT PMD in DPDK
> 
> Hi Alex,
> 
> >  [changchun] Many thanks! So from this limitation, we can conclude
> > that Lcore can only dequeue the QAT queue which was enqueued by
> > itself, right. If so, then the Crypto device lib doc may be a little misleading, at least some notes
> should be put there.
> [Fiona] Limitations are generally on the device documentation - it wouldn't make sense to pollute the
> lib with the limitations of individual devices. (though I understand it's easy to miss the limitations) As
> mentioned before, if this is an important use-case for you we would be interested in hearing about it,
> and we could investigate performant ways to remove the limitation.
> 
>  [changchun] Currently we don't see if it is necessary to remove this limitation or not. But we do need
> to confirm what the relationship between logical core, queue pair, and crypto device. As my
> understanding, no matter pipe line or current limitation, the QAT accepts the request from the RX
> queue of a queue pair and after the processing, the data will be put the TX queue on the same queue
> pair, it is right? Say enqueue data to the RX queue of Queue pair 1, the return data would always be
> put to the TX queue of Queue pair 1, not possible to other Queue pair's TX queue, right? Let me know
> if you did not get my question.

[Fiona] well, we use names tx and rx the opposite way you named them - but this doesn't matter as neither
tx nor rx names are visible on the API. Just qp_id. So whatever qp_id you enqueue to, you will get the response
on the same qp_id in a subsequent dequeue operation. And they will be dequeued in same order as you enqueued.  



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