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Felix Geisendörfer 2022-02-10 00:40:59 +01:00 committed by GitHub
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@ -242,7 +242,7 @@ There are a few known issues and limitations of the CPU profiler that you might
- 🐞 Profiler labels in Go versions <= 1.17 suffered from several bugs.
- [GH #48577](https://github.com/golang/go/issues/48577) and [CL 367200](https://go-review.googlesource.com/c/go/+/367200/): Labels were missing for goroutines executing on the system stack, executing C code, or making system calls.
- [CL 369741](https://go-review.googlesource.com/c/go/+/369741): The first batch of samples in a CPU profile had an off-by-one error causing a misattribution of labels.
- [CL 369984](https://go-review.googlesource.com/c/go/+/369984): System goroutines created on behalf of user goroutines (e.g. for garbage collection) incorrectly inherited their parents labels.
- [CL 369983](https://go-review.googlesource.com/c/go/+/369983): System goroutines created on behalf of user goroutines (e.g. for garbage collection) incorrectly inherited their parents labels.
- ⚠️️ You can call [`runtime.SetCPUProfileRate()`](https://pkg.go.dev/runtime#SetCPUProfileRate) to adjust the CPU profiler rate before calling `runtime.StartCPUProfile()`. This will print a warning saying `runtime: cannot set cpu profile rate until previous profile has finished`. However, it still works within the limitation of the bug mentioned above. This issue was [initially raised here](https://github.com/golang/go/issues/40094), and there is an [accepted proposal for improving the API](https://github.com/golang/go/issues/42502).
- ⚠️ The maximum number of nested function calls that can be captured in stack traces by the CPU profiler is currently [`64`](https://sourcegraph.com/search?q=context:global+repo:github.com/golang/go+file:src/*+maxCPUProfStack+%3D&patternType=literal). If your program is using a lot of recursion or other patterns that lead to deep stack depths, your CPU profile will include stack traces that are truncated. This means you will miss parts of the call chain that led to the function that was active at the time the sample was taken.