@isidorn change looks good and makes sense to me.

@rsalvador Thanks a lot for your PR. I left comments directly in the code, once you address those we could merge this in.
I am assigning this to the march milestone since next week we are wrapping up our february release and are only accepting limited changes.

@rsalvador Also before we accpet this change I would still need convincing vscode blocks the UI. Since I like what we are already doing - we are refreshing the callstack view with a 50ms delay. So if multiple changes come in that range we will only refresh once. Do you still see the vscode blocking if you change this 50ms to 200 ms for example here https://github.com/Microsoft/vscode/blob/master/src/vs/workbench/parts/debug/electron-browser/callStackView.ts#L82

Including @testforstephen to see if this can be fixed on the Java extension side. Even though vscode UI should protect against such behavior from an extension.

@isidorn thank for looking into this!
vscode still blocks when changing 50ms to 200ms in callStackView.ts
the reason is because the perf problem occurs even before callStackView.ts is invoked, the code hogging the cpu seem to be the calculations between the calls to fetchThreads() in debugService.ts and the actual request of the refresh in callStackView.ts

All CLA requirements met.

@rsalvador thanks for more details. I will look into this in greater details next week. Until then we can also get @testforstephen feedback

Looks good. The fix could help to reduce the threadsRequest frequency to JVM. Especially during remote debugging, the network perf has a big impact on the response speed of each vscode debug request, reducing the threadsRequest frequency will improve the perf a lot. In a classic modern Java micro service, such as SpringBoot, they have more than 20 threads in running after started, that means there are 20 threadsRequests sent to the debugger during the debug session initialization. This give bad performance for remote debugging.

@rsalvador I have commented in the code - mostly polish.
Also you would need to resolve conflicts in order for this to be merged.
Thanks

@isidorn performed all changes and rebased/resolved

@rsalvador thanks a lot. Looks good to me, let's merge it in.