JitStatsDiagnoser

[adamsitnik]

I'm currently working on improving System.CommandLine (mainly design, but also perf).

One of the things unique about S.CL is that it's typically used just once, during process startup time. So what matters is the number of JIT compilations. I've implemented this simple diagnoser that prints simple JIT stats.

Sample usage:

dotnet run -c Release -f net7.0 --filter *IntroBasic.Sleep --profiler jit

Method	Mean	Error	StdDev	Methods JITted	Methods Tiered	JIT allocated memory
Sleep	15.53 ms	0.034 ms	0.032 ms	1,102	15	221,736 B

@AndyAyersMS @kunalspathak @stephentoub @EgorBo @kouvel I am opened to extending it, but I need your feedback before I invest my time. I know that PerfView offers more:

[adamsitnik]

Also, I am not sure if TieredCompilationBackgroundJitStart is just "methods tiered" or "the number of times tiered JIT kicked in and started working"

[kunalspathak]

Thanks @adamsitnik . This should definitely help us in reproing and investigating performance issues. We can add more columns as and when we have a need, but this is a good starter.

[EgorBo]

@adamsitnik nice! Methods JITted includes both tier0 and tier1, right?

[adamsitnik]

Methods JITted includes both tier0 and tier1, right?

This is the number of MethodJittingStarted CLR events (that is all I know right now).

[EgorBo]

Ah, right.
Also, it'd be nice for the diagnoser to generate a MethodsJitted.md report that will list all the methods jitted 🙂 can probably contribute that myself if you think it makes sense

[adamsitnik]

think it makes sense

I do, please go ahead and send a PR.

BTW I was also wondering whether we should filter the methods by namespace and for example remove all BenchmarkDotNet* methods from the report.

[kouvel]

Also, I am not sure if TieredCompilationBackgroundJitStart is just "methods tiered" or "the number of times tiered JIT kicked in and started working"

This event is emitted when a background thread starts jitting to tier up and includes info about how many methods were pending jitting at that time. The corresponding Stop event is emitted when the background thread stops jitting, and includes info about how many methods were jitted between the Start/Stop events and how many methods are still pending jitting.

[adamsitnik]

@kouvel big thanks for the feedback! I've sent a fix, PTAL: #2246

[KeterSCP]

Are there any plans to make this diagnoser available via attribute?

[adamsitnik]

@KeterSCP There are not, but you can send a PR that adds such an attribute. Here you can find existing attributes for similar diagnosers: https://github.com/dotnet/BenchmarkDotNet/tree/master/src/BenchmarkDotNet.Diagnostics.Windows/Configs