Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [RFC PATCH v4 2/6] perf stat: Fork and launch perf record when perf stat needs to get retire latency value for a metric. | Date | Tue, 12 Mar 2024 17:03:19 -0700 |
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weilin.wang@intel.com writes:
> From: Weilin Wang <weilin.wang@intel.com> > > When retire_latency value is used in a metric formula, perf stat would fork a > perf record process with "-e" and "-W" options. Perf record will collect > required retire_latency values in parallel while perf stat is collecting > counting values.
How does that work when the workload is specified on the command line? The workload would run twice? That is very inefficient and may not work if it's a large workload.
The perf tool infrastructure is imho not up to the task of such parallel collection.
Also it won't work for very long collections because you will get a very large perf.data. Better to use a pipeline.
I think it would be better if you made it a separate operation that can generate a file that is then consumed by perf stat. This is also more efficient because often the calibration is only needed once. And it's all under user control so no nasty surprises.
-Andi
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