Document how to measure iOS startup times

[jonathanpeppers]

Just like the amazing doc here:

• https://github.com/xamarin/xamarin-macios/wiki/Profiling

I think we need one on measuring iOS startup times? And perhaps other Apple platforms?

We have this document from Apple using instruments:

• https://developer.apple.com/documentation/xcode/reducing-your-app-s-launch-time

But I think there is some slowdown once you attach instruments to an iOS app (as seen in dotnet/maui#7687).

We did this for the measurements at https://aka.ms/dotnetperfstatus

• Implement iOS startup time tracing dotnet/performance#2355
• Add --fully-drawn-magic-string option to startup scenario dotnet/performance#2404

If we make a new doc, we can link to it from:

• https://github.com/dotnet/maui/wiki/Profiling-.NET-MAUI-Apps

[jonathanpeppers]

Also probably want MacCatalyst included here, too. But that might be a completely different topic?

[art-denisov]

I've tried to follow your instructions on the blog

But when I try to run dotnet-trace in a following way:

dotnet-trace collect --diagnostic-port /tmp/maui-app,connect --format speedscope

I've got an error:

Do you have some advice for me? What have I done wrong?

[art-denisov]

Also, I've tried to do steps like in the guide for android

1. Start dotnet-dsrouter
   dotnet-dsrouter client-server -tcps 127.0.0.1:9001 -ipcc /tmp/maui-app --forward-port iOS
2. Start dotnet-trace without a connection
   dotnet-trace collect --diagnostic-port /tmp/maui-app --format speedscope
3. Run the iOS app on a physical device
   mtouch --launchdev TestMauiPerf.app --wait-for-exit --argument --connection-mode --argument none '--setenv:DOTNET_DiagnosticPorts=/tmp/maui-app'

So, when I run dotnet-trace I've got a message like for an android session:

Then I launched iOS app and it just runs on my iPhone, but dotnet-trace hasn't caught any data and is still waiting for a connection.

How could I profile maui iOS apps?

[art-denisov]

@jonathanpeppers can you comment on my questions somehow?

[rolfbjarne]

@art-denisov try following this guide for profiling iOS apps: https://github.com/xamarin/xamarin-macios/wiki/Profiling

[art-denisov]

I have already tried it. But, as I described above, I got an error on the last step.

When I ran the following command
dotnet-trace collect --diagnostic-port /tmp/maui-app,connect --format speedscope

What have I missed?

I should notice that I try to do it on mac with the physical device connected by the cable.

[rolfbjarne]

@art-denisov two things:

1. You have to launch the app first, wait for certain output, then execute the dotnet-trace collect ... command.

2. Your DOTNET_DiagnosticPorts variable is wrong, it should be:

   mtouch --launchdev TestMauiPerf.app --wait-for-exit --argument --connection-mode --argument none '--setenv:DOTNET_DiagnosticPorts=127.0.0.1:9001,suspend,listen'

[rolfbjarne]

A doc about how to measure startup on iOS is up: https://github.com/xamarin/xamarin-macios/wiki/Profiling-App-Launch

If we make a new doc, we can link to it from:
dotnet/maui/wiki/Profiling-.NET-MAUI-Apps

Done.

[art-denisov]

@rolfbjarne
I've tried to follow your recommendations and unfortunately, it doesn't work still

I use the command that you correct
mtouch --launchdev TestMauiPerf.app --wait-for-exit --argument --connection-mode --argument none '--setenv:DOTNET_DiagnosticPorts=127.0.0.1:9001,suspend,listen'
and wait for the output

The runtime has been configured to pause during startup and is awaiting a Diagnostics IPC ResumeStartup command from a Diagnostic Port

but it didn't show up. My terminal looked like

[rolfbjarne]

@art-denisov did the app launch/show up on the device and if so, can you use it/interact with it?

[art-denisov]

The app launches on the device and hangs on the start splash screen. I can't interact with it. It seems like the app waits for something.

If I remove suspend,listen at the end of the command the launches normally and I can use it.

[rolfbjarne]

@art-denisov which version of dotnet-dsrouter do you have?

$ dotnet-dsrouter --version
6.0.345601+f73f09031cebfc6256a9029ce9285a52fdad7380

If you have an earlier version, you need to update it like this: dotnet/diagnostics#3134 (comment)

Also, once the app is running (and non-responsive), what happens if you execute the dotnet-trace command?

$ dotnet-trace collect --diagnostic-port /tmp/maui-app,connect --format speedscope
???

[art-denisov]

I checked the version of dotnet-dsrouter and dotnet-trace. It's equal to the version in your answer

So, I tried to follow your instruction:

1. Run dotnet-dsrouter
   

2. Launch the app on the physical device
   
   As I wrote before, the app has launched successfully and waited on the splash screen.

3. Run dotnet-trace
   
   It didn't collect data, just the error as I marked in my first comment.

[rolfbjarne]

@art-denisov looks like there's a copy-paste error in the instructions, try using the following dotnet-dsrouter command instead:

dotnet-dsrouter server-client -tcpc 127.0.0.1:9001 -ipcs /tmp/maui-app --forward-port iOS

(and then the other commands stay the same)

[art-denisov]

So, it helped.
But it still works strangely.

When I run the command
dotnet-trace collect --diagnostic-port /tmp/maui-app,connect --format speedscope
It collects some data but immediately completes the tracing. Although, I haven't pressed or <Ctrl+C>.

The app on the phone becomes fully interactive.

If I try to execute the command again without relaunching the app, I've got the error.

[rolfbjarne]

That looks like a problem in dotnet-trace. Maybe try not passing --format speedscope, since it looks like that might be related:

dotnet-trace collect --diagnostic-port /tmp/maui-app,connect

[art-denisov]

It still completes the tracing immediately but without errors.

[rolfbjarne]

That's weird...

• Does the resulting trace file contain anything?
• Is anything printed in the tab running mlaunch --launchdev ...?