how to detect heavy task by instrument?

my app randomly has been terminated by IOS at some time.

Data Source: Microstackshots
Shared Cache: 0x36a90000 F409EE7C-4825-377F-B10A-B53F999FA728

Command: VCS
Path: /private/var/containers/Bundle/Application/A71F3652-CBE2-4B12-A591-78B53C98EF0A/myapp.app/myapp
Version: 3.8.0 (3.8.0.2629)
Beta Identifier: 4DD81AC4-16E8-4B51-A4FE-D51FE71935F4
PID: 748

Event: cpu usage
Action taken: Process killed
CPU: 9 seconds cpu time over 9 seconds (100% cpu average), exceeding limit of 60% cpu over 15 seconds
CPU limit: 9s
Limit duration: 15s
CPU used: 9s
CPU duration: 9s
Duration: 9.02s
Duration Sampled: 4.92s
Steps: 3

Hardware model: iPhone12,1
Active cpus: 6


Heaviest stack for the target process:
3 ??? (libsystempthread.dylib + 14100) [0x1b6c03714]
3 ??? (libdispatch.dylib + 80168) [0x1b6bac928]
3 ??? (libdispatch.dylib + 46304) [0x1b6ba44e0]
3 ??? (libdispatch.dylib + 131152) [0x1b6bb9050]
3 ??? (libdispatch.dylib + 131376) [0x1b6bb9130]
3 ??? (libsystemkernel.dylib + 166176) [0x1b6ce4920]


What is best way to detect heavy task by instruments ?

I have tried, but I can't see which part cause this issue?

BTW: I see the heavy task is audio session, but cause my app is voip, and only when app runs in background receive PUshkit to get CallKit, it will occur

Thanks,