go-profiler-notes/stack-traces.md

Stack Traces in Go

Stack traces play a critical role in Go profiling. So let's try to understand them to see how they might impact the overhead and accuracy of your profiles.

Introduction

All Go profilers work by collecting samples of stack trace and putting them into pprof profiles. Ignoring some details, a pprof profile is just a frequency table of stack traces like shown below:

stack trace	count
main;foo	5
main;foo;bar	3
main;foobar	4

Let's zoom in on the second stack trace in the table above: main;foo;bar. A Go developer will usually be more familiar with seeing a stack trace like this as rendered by panic() or runtime.Stack() shown below:

goroutine 1 [running]:
main.bar(...)
	/path/to/go-profiler-notes/examples/stack-trace/main.go:17
main.foo(...)
	/path/to/go-profiler-notes/examples/stack-trace/main.go:9
main.main()
	/path/to/go-profiler-notes/examples/stack-trace/main.go:5 +0x3a

This text format has been described elsewhere so we won't discuss the details of it here. Instead we'll dive even deeper and ask ourselves where this data is coming from.

Goroutine Stack

Stack traces

Stack Unwinding

Frame Pointers

To write ...

.gopclntab

To write ...

DWARF

To write ...

Symbolization

Woho

Overhead

To write ...

Accuracy

To write ...