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I didn't mean just WASM -> JS but the WebGL API call overhead which includes marshalling the call from WASM runtime across multiple layers and processes inside

by samiv 2y ago

I didn't mean just WASM -> JS but the WebGL API call overhead which includes marshalling the call from WASM runtime across multiple layers and processes inside the browser. Win32 performance counter has native resolution < 1us OffScreencanvas is something I haven't actually come across before. Looks interesting, but I already expect that the API is either brain damaged or intentionally nerfed for security reasons (or both). Anyway I'll look into it so thanks for that!

flohofwoe 2y ago
> Win32 performance counter has native resolution < 1us Yes but that's hardly useful for things like measuring frame duration when the OS scheduler runs your per-frame code a millisecond late or early, or generally preempts your thread in the middle of your timing code (eg measuring durations precisely is also a non-trivial problem on native platforms even with high precision time sources).
- MindSpunk 2y ago
  Almost every game for the last 25 years has used those Win32 performance counters, or the platforms nearest equivalent (it’s a just a wrapper over some CPU instructions), to measure frame times. It’s the highest resolution clock in the system, it’s a performance counter. You’re supposed to use it for that. If you want to correlate the timestamps with wall time then good luck, but if you just need to know how many nanoseconds elapsed between two points in the program on a single thread then that’s your tool.
  - flohofwoe 2y ago
    Almost all games also had subtle microstutter until some Croteam peeps actually looked into it and figured out what's wrong with naive frame timing on modern operating systems: https://medium.com/@alen.ladavac/the-elusive-frame-timing-168f899aec92 https://medium.com/@alen.ladavac/the-elusive-frame-timing-16...) TL;DR: the precision of your time source won't matter much since thread scheduling gets in the way, one general solution is to apply some sort of noise filter to remove jitter

by samiv 2y ago

flohofwoe 2y ago

> Win32 performance counter has native resolution < 1us Yes but that's hardly useful for things like measuring frame duration when the OS scheduler runs your per-frame code a millisecond late or early, or generally preempts your thread in the middle of your timing code (eg measuring durations precisely is also a non-trivial problem on native platforms even with high precision time sources).

MindSpunk 2y ago
Almost every game for the last 25 years has used those Win32 performance counters, or the platforms nearest equivalent (it’s a just a wrapper over some CPU instructions), to measure frame times. It’s the highest resolution clock in the system, it’s a performance counter. You’re supposed to use it for that. If you want to correlate the timestamps with wall time then good luck, but if you just need to know how many nanoseconds elapsed between two points in the program on a single thread then that’s your tool.
- flohofwoe 2y ago
  Almost all games also had subtle microstutter until some Croteam peeps actually looked into it and figured out what's wrong with naive frame timing on modern operating systems: https://medium.com/@alen.ladavac/the-elusive-frame-timing-168f899aec92 https://medium.com/@alen.ladavac/the-elusive-frame-timing-16...) TL;DR: the precision of your time source won't matter much since thread scheduling gets in the way, one general solution is to apply some sort of noise filter to remove jitter