RE: [PATCH for-next 09/10] IB/mlx4: Add timestamp_mask and hca_core_clock to query_device

Hefty, Sean
2015-05-29T17:09:14Z

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> Now, as a general rule, I would call timestamps general. They should be
> added in a fashion that anyone can implement. They should also be well
> defined. Sean's questions raise a very valid point. Exactly what is
> being timestamped, and do we care about different timestamp options? Is
> it completion of message, start of message, transfer from HCA to main
> system memory completion, etc. The 00/10 header to this patch series
> was probably answering Sean's question, but just based on the name of
> the TIMESTAMP flag to the CQ creation attr struct it isn't clear that
> this is the case.

I didn't see the information that I was looking for in the patch header to this series. As Jason pointed out, the use case is lacking.

IMO, it could make just as much sense to associate/enable time stamping with the QP as with the CQ, or even make it configurable per operation or operation type.

If Christoph has a clear use case and wants to go to the 'bare metal', then a vendor specific option seems ideal. At least until there are other implementations or the driving use case is clearer.

- Sean
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