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 performance#2355
• Add --fully-drawn-magic-string option to startup scenario 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.