Waiting for go1.21: Execution Tracing with < 1% Overhead

Go’s execution tracer (aka go tool trace) has suffered from high overhead since its inception in 2014. Historically this has forced potential users to worry about up to 20% of CPU overhead when turning it on. Due to this, it's mostly been used in test environments or tricky situations rather than gaining adoption as a continuous profiling signal in production.

However, in early 2023 my colleague Nick Ripley and I started to become convinced that we could change this by implementing frame pointer unwinding. You can read more about the details in the blog post below:

Reducing Go Execution Tracer Overhead With Frame Pointer Unwinding

Learn how frame pointer unwinding could significantly reduce the CPU overhead of the Go execution tracer.

Felix GeisendörferFelix Geisendörfer

Since then we’ve been actively collaborating with the Go runtime team at Google, in particular Michael Knyszek, Michael Pratt and Cherry Mui in order to make this a reality. And at this point it looks like we’ve succeeded: The go1.21 release coming out in ~August will feature a new version of the tracer which should provide less than 1% overhead for most applications 🥳 (see upcoming release notes).

Below is a list of directly or indirectly related patches that contributed to this effort:

• 2023-03-13 runtime: remove NOFRAME from asmcgocall, systemstack and mcall (Quim Muntal)
• 2023-03-30 runtime: fix frame pointer loop on amd64 (Felix Geisendörfer)
• 2023-03-30 runtime/trace: enable frame pointer unwinding on amd64 (Felix Geisendörfer)
• 2023-03-30 runtime/trace: use regular unwinding for cgo callbacks (Felix Geisendörfer)
• 2023-03-30 runtime: add a benchmark of FPCallers (Felix Geisendörfer)
• 2023-04-04 runtime/trace: Fix TestTraceSymbolize on solaris and illumos (Felix Geisendörfer)
• 2023-04-05 runtime: save frame pointer to the stack in signal handlers for arm64 (Nick Ripley)
• 2023-04-19 runtime: adjust frame pointer on stack copy on ARM64 (Cherry Mui)
• 2023-04-20 runtime: turn frame pointer unwinding for tracing off by default (Nick Ripley)
• 2023-04-28 runtime/trace: avoid frame pointer unwinding for events during cgocallbackg (Nick Ripley)
• 2023-04-30 runtime: fix systemstack frame pointer adjustment (Felix Geisendörfer)
• 2023-05-02 runtime/trace: enable frame pointer unwinding by default for amd64 and arm64 (Nick Ripley)
• 2023-05-03 runtime: add test for systemstack frame pointer adjustment (Felix Geisendörfer)
• 2023-05-03 runtime: remove systemstack logic from adjustframe (Felix Geisendörfer)
• 2023-05-12 runtime: remove unused skip arg from fpTracebackPCs (Felix Geisendörfer)
• 2023-05-22 runtime: rename getcallerfp to getfp (Felix Geisendörfer)

So if you're into Go performance and observability, this improvement is definitely something to look forward to.

And this is just the beginning:

1. Michael Knyszek has proposed a lot of exciting improvements that will further improve execution tracing in upcoming releases.
2. Dominik Honnef's gotraceui viewer keeps improving.
3. We've also been busy with integrating the execution tracer into our profiling product at Datadog. We'll share more information about this soon.