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jlfwong / speedscope

🔬 A fast, interactive web-based viewer for performance profiles.
https://www.speedscope.app
MIT License
5.45k stars 237 forks source link

Clarify specification of startValue in speedscope file format #464

Closed tom93 closed 7 months ago

tom93 commented 7 months ago

The spec confused me and I'd like to clarify it. Please check that my understanding is correct!

From the commit message:

The previous description ("event values will be relative to this startValue") was ambiguous.

Suppose the profile starts at wall time 1000ms and the first event is at wall time 1003ms.

The intention is that startValue should be set to 1000 and the "at" value of the event should be set to 1003. The viewer's time axis will start at 0ms and the first event will be displayed at 3ms.

But the previous description could be incorrectly interpreted as saying that the "at" value of the first event should be set to 3 (the time relative to startValue, as opposed to the absolute wall time).

Clarify that "relative" is referring to how the viewer displays the data, not about which values to store in the file.

jlfwong commented 7 months ago

Thanks!