How to profile on Android?

[MaxGyver83]

I try to write a Markdown viewer for Android with Fyne. So far, it's super slow: After selecting a folder and clicking the "grant permission" button, it takes about 10 seconds to display the rendered file content (of the first file in the folder). (10 seconds is for a release build using Fyne's develop branch.) On the desktop (Linux), a Markdown file is displayed instantly.

I have tried to profile the app with "github.com/pkg/profile". This works on Linux but on Android I don't know how to use it.

When I set no profile path, I can't find the profile file. I guess it's in the app's data folder which I can't access (because my device is not rooted).

When I set an accessible directory, the app hangs right after starting (I see only the large icon):

func main() {
	defer profile.Start(profile.ProfilePath("/storage/self/primary/Download/")).Stop()
	a = app.New()

Am I using the wrong tool? Or just the wrong profile path? How do you profile Fyne apps on Android?

Update:

I think the problem was that /storage/self/primary/Download/cpu.pprof already existed. After deleting it, I could start my app and a new cpu.pprof was created. But the new file has a size of 0 bytes. Maybe this error is related!?

02-19 10:12:38.965 25167 25167 E ANR_LOG : >>> msg's executing time is too long
02-19 10:12:38.965 25167 25167 E ANR_LOG : Blocked msg = { when=-7s943ms what=0 target=android.view.Choreographer$FrameHandler callback=android.view.Choreographer$FrameDisplayEventReceiver } , cost  = 7943 ms
...

[MaxGyver83]

I cound find a way:

Create a global variable

var (
	prof  interface{ Stop() }
)

Start the profiler

func main() {
	prof = profile.Start(profile.ProfilePath("/sdcard/Download/"))
	a = app.New()

Stop the profiler manually on a button click

	myButton.OnTapped = prof.Stop

Copy the file over to my laptop

$ adb pull /sdcard/Download/cpu.pprof

Profiler output

$ go tool pprof -top ./cpu.pprof
...
Duration: 36.08s, Total samples = 23.53s (65.21%)
Showing nodes accounting for 19.51s, 82.92% of 23.53s total
Dropped 581 nodes (cum <= 0.12s)
      flat  flat%   sum%        cum   cum%
     2.72s 11.56% 11.56%     10.04s 42.67%  golang.org/x/image/vector.(*Rasterizer).rasterizeOpOver
     1.57s  6.67% 18.23%      1.57s  6.67%  [libc.so]
     1.22s  5.18% 23.42%      1.22s  5.18%  [libart.so]
     1.14s  4.84% 28.26%      1.17s  4.97%  runtime.cgocall
     1.07s  4.55% 32.81%      1.07s  4.55%  runtime.futex
     0.98s  4.16% 36.97%      1.01s  4.29%  image/draw.drawNRGBAOver
     0.90s  3.82% 40.80%      1.70s  7.22%  runtime.mallocgcTiny
     0.81s  3.44% 44.24%      0.81s  3.44%  image/color.NRGBA.RGBA
     0.78s  3.31% 47.56%      1.33s  5.65%  image/color.nrgbaModel
     0.75s  3.19% 50.74%      2.45s 10.41%  image.(*NRGBA).Set
     0.66s  2.80% 53.55%      2.87s 12.20%  runtime.mallocgc
     0.62s  2.63% 56.18%      0.79s  3.36%  image.(*NRGBA).NRGBAAt
     0.51s  2.17% 58.35%      3.04s 12.92%  runtime.convTnoptr
     0.50s  2.12% 60.48%      0.64s  2.72%  golang.org/x/image/vector.(*Rasterizer).floatingLineTo
     0.44s  1.87% 62.35%      0.44s  1.87%  golang.org/x/image/vector.floatingAccumulateMask (inline)
     0.32s  1.36% 63.71%      0.33s  1.40%  runtime.nextFreeFast (inline)
     0.29s  1.23% 64.94%      0.29s  1.23%  [libGLES_mali.so]
...

[andydotxyz]

To find out a writable location use app.Storage().RootURI().
When I am debugging I use pprof and the HTTP server so I can connect remotely.

[MaxGyver83]

To find out a writable location use app.Storage().RootURI().

I have tried this. I get this folder: file:///data/user/0/com.example.myapp/files/fyne
Unfortunately, I have no read permission for this folder on Android (ls returns "Permission denied").

When I am debugging I use pprof and the HTTP server so I can connect remotely.

This sounds interesting! I'll try this. Thank you!

[andydotxyz]

I have tried this. I get this folder: file:///data/user/0/com.example.myapp/files/fyne
Unfortunately, I have no read permission for this folder on Android (ls returns "Permission denied").

What call is failing? That space is read/write for the app, always.
Perhaps listing is not permitted, but you could try making a sub-directory so you have complete control.