Vtune Metrics discrepancy (uOps vs Instructions)

[Donghyeon]

Hello. 

I am currently in academics and profiling Transformer performance on VTune. 

The metrics used on the results of microarchitecture exploration are mostly "% of pipeline slots" entering the front end and exiting the back end, thus relative to the number of uOps, or microcode. 

And yet the foremost two results are  "Instructions retired" and "CPI Rate", based on the number of 'instructions' which I understood as instruction BEFORE being decoded into uOps.  

I'm having a hard time understanding why the metrics aren't unified into either using uOps-only or Instructions-only. I think the logical choice would be using uOps-based metric as computing resources operate on uOp-level. Then shouldn't "Cycle per uOp" and "uOps retired" be a more readily used metric? 

[JyothisV_Intel]

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Jyothis V James

[Dmitry_R_Intel1]

In general I would agree - metrics in uops better characterize any particular microarchitecture. But uops are very microarchitecture-specific. So metrics in retiring instructions still make sense and quite useful when you want to compare cross-microarchitecture or even cross-architecture. E.g. if you compare Intel Icelake with Intel Haswell or some Intel CPU with AMD CPU or ARM CPU.

[JyothisV_Intel]

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Jyothis V James

[JyothisV_Intel]

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Jyothis V James