Re: [PATCH for-next V2 0/9] Add completion timestamping support

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On Mon, Jun 01, 2015 at 01:00:57PM -0400, Doug Ledford wrote:
> > case for this feature, generalizing too much may destroy the
> > performance that is valuable here.
 
> I'm not convinced of that.  Steve has already spoke up about the
> timestamps available in cxgb4.  Those are very different and yet still
> highly valuable to someone investigating performance of their RDMA
> application.

? cxgb4 looks nearly identical to me. There is only one HW time stamp
'cqe_sge_ts', which occurs at some point in the flow, and is written
the CQE. The current cycle counter can be read from SGE_TIMESTAMP_LO
registers. Same as mlx4, really.

The rest is just bookkeeping and logging that doesn't require special
verbs support for an app to implement.

Jason
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