[BUG] Major frames per second drops on 2.88.0

[imerzan]

Description

My application goes from running at 30-32 FPS (on a 30hz refresh w/ vsync) down to 20 FPS after updating from 2.80.4 to 2.88.0

Using SKGLControl in WinForms .NET6

After I downgraded back to 2.80.4 my issue went away completely with no code changes.

// Vsync enabled on SKGLControl

  private async void MainForm_Shown(object sender, EventArgs e)
  {
      while (glControl.GRContext is null) await Task.Delay(1); // Wait for GL Context to be set
      glControl.GRContext.SetResourceCacheLimit(503316480); // Fixes low FPS on extra big bitmaps
      while (true)
      {
          await Task.Run(() => Thread.SpinWait(50000)); // Delay between each frame
          glControl.Refresh(); // draw next frame
      }
  }

private void SKGLCONTROL_PaintSurface(object sender, SKPaintGLSurfaceEventArgs e)
{
	SKCanvas canvas = e.Surface.Canvas; // get Canvas reference to draw on
	canvas.Clear(); // Clear canvas
	canvas.DrawBitmap(); // Draw a cached bitmap on each render, roughly 3000x3000 resolution bitmap PNG
	// draw some lines , circles, etc. less than 1000 items
	canvas.Flush(); // commit frame to GPU
}

Expected Behavior

I expect to get around ~30 FPS like the previous version.

Actual Behavior

I am getting 20 FPS.

Basic Information

• Version with issue: 2.88.0
• Last known good version: 2.80.4
• IDE: VS 2022
• Platform Target Frameworks: WinForms .NET6 win-x64

[MichalJan008]

Performance drop seems to be dependant of the bitmap size. For me, instead of getting c.a. 50 fps, Now I get c.a. 10, or even less - when working with 42 Megapixel SkBitmap - what is a blocker for the app. I've recorded a screen capturing - for 2.80.4 and for 2.88.0 on iPhone 11. I'l try to upload somewhere and share the links.

[MichalJan008]

2.80.4 (fast) https://youtu.be/ZN3ki_IpPUg

2.88.0 (slow) https://youtu.be/jNvGh4R19cA

[mattleibow]

Could you attach a small repro that I can use to debug the process? Mainly I think I need some large images and some drawing code.

This appears to be the same as #2188, but this says GPU/GL and that is using raster. Not sure if this is a sign of bitmap drawing slow, or some GPU things.

Also some machine hardware numbers - like GPU model/spec.

[imerzan]

@mattleibow skiasharp-bug-example-master.zip Here is a small repro, contains a good sized Bitmap

I turned off VSync to better demonstrate the frames per second differences when uncapped. Most apparent when the Window is maximized.

2.80.4 ~300 FPS

2.88.0 ~ 100 FPS

I am using a Dell Optiplex 7050 I7-7700 CPU Intel HD Graphics 630

in a Remote Desktop Session

Hope this helps

[mattleibow]

I am wondering if it is actually this change in 82:

 Removed drawBitmap and related functions from SkDevice; all public drawBitmap functions on SkCanvas automatically wrap the bitmap in an SkImage and call the equivalent drawImage function. Drawing mutable SkBitmaps will now incur a mandatory copy. Switch to using SkImage directly or mark the bitmap as immutable before drawing.

https://github.com/mono/skia/blob/xamarin-mobile-bindings/RELEASE_NOTES.txt#L369-L372

[imerzan]

I am wondering if it is actually this change in 82:

Removed drawBitmap and related functions from SkDevice; all public drawBitmap functions on SkCanvas automatically wrap the bitmap in an SkImage and call the equivalent drawImage function. Drawing mutable SkBitmaps will now incur a mandatory copy. Switch to using SkImage directly or mark the bitmap as immutable before drawing.

https://github.com/mono/skia/blob/xamarin-mobile-bindings/RELEASE_NOTES.txt#L369-L372

Bingo! That was it.

[mattleibow]

What changes did you make to get that sweet sweet speed back? Just using SkImage?

[imerzan]

What changes did you make to get that sweet sweet speed back? Just using SkImage?

I ended up just making my SKBitmaps immutable :) worked perfectly per the referenced solution you posted