Windows and WASM performance

[benc-uk]

I'm building a CHIP-8 emulator in Go using ebiten

I've spent quite a lot of time optimizing performance, esp for my rendering and how I output the display. My graphics are incredibly basic, just a monochrome 64x32 image (1-bit so pixels are either on or off) which is then output scaled to the screen inside the Draw() function. I'm seeing a few things

I'm seeing a couple of things:

• On Linux (WSL2) everything performs extremely well, so much so I have to slow the emulator processor loop down quite a lot to make programs playable
• Windows is significantly slower, I have to set vsync disabled and ebiten.UncappedTPS set to make things playable even then it's not great. The difference here is not slight, it's probably several orders of magnitude, which I don't think is down to my code.
• WASM is even slower still, I'm using 1000 x 500 output size which doesn't seem too outrageous, but nothing is really playable, everything just crawls

My question is ebiten really only optimised for Linux? Should I continue trying to tune my code or is the slower performance on Windows and WASM a known problem?

[hajimehoshi]

My question is ebiten really only optimised for Linux?

No, the program should work well on Windows as well. Could you share the code? Thanks!

[benc-uk]

I think the culprit is the sleep I have inside my main emulator processor fetch/execute loop
If I remove it, the Windows version runs extremely fast (as you might expect)
If I add even a very small sleep e.g. time.Sleep(time.Duration(1) * time.Nanosecond) it slows to a crawl

I'm going to carry on investigating but for now I'm about 99% confident this is not an ebiten issue. Sorry for wasting your time.
If discover anything interesting or a solution I'll let you know

[hajimehoshi]

Aha. As far as I know, the precision of Windows timer is not very good and this can be more than 1-10 [ms] even though you specify 1[us] or less. It is surprising to me that WSL emulates more accurate timers for Linux.

I'm going to carry on investigating but for now I'm about 99% confident this is not an ebiten issue. Sorry for wasting your time.

No problem, thank you for reporting!

[benc-uk]

I found this
golang/go#44343

As for WSL, it's basically "full" Linux system now, just running inside a thin virtual machine, so to most purposes it works just like Linux

PS. Forgot to say, I love Ebiten, keep up the awesome work!

[benc-uk]

As a follow up, I've removed my separate processor loop and goroutine, and no longer rely on a sleep. I now do everything from within the ebiten Update loop, executing multiple CPU cycles inside that loop to speed things up. This has solved nearly all of the issues I was having with performance on Windows and even WASM is fully playable now

[hajimehoshi]

Great! I'm pretty happy to hear that your application with Ebiten worked well. Thank you for reporting!