Sampling profiling not working?

[arvid-norlander]

I do not get CPU samples from my program using these bindings (on Ubuntu 24.04), and I can't figure out what I'm doing wrong. I don't have Windows or MacOS to test with.

I can do sampling profiling perfectly well using perf as the same user. I'm not running under docker. So it is not a permission problem. And as far as I can tell, the client is built with sampling support enabled. Tracing spans works correctly.

It seems to use the correct features? As output by cargo add:

      Adding tracing-tracy (workspace) to optional dependencies
             Features as of v0.11.4:
             + broadcast
             + callstack-inlines
             + code-transfer
             + context-switch-tracing
             + debuginfod
             + enable
             + sampling
             + system-tracing
             - delayed-init
             - demangle
             - fibers
             - flush-on-exit
             - manual-lifetime
             - ondemand
             - only-ipv4
             - only-localhost
             - timer-fallback
             - verify

I don't know how to debug this further. According to upstream docs it should be used automatically when possible, assuming the support was enabled as build time.

If there isn't anything I have missed: I guess the next step would be to write a simple C++ program that just loops and uses tracy directly to see if that works?

• Ubuntu 24.04
• Kernel 6.8.0-41-generic
• 12th Gen Intel(R) Core(TM) i9-12950HX

[arvid-norlander]

Update: figured it out. kernel.perf_event_max_sample_rate needs to be at least 10000. It would be good TRACY_SAMPLING_HZ could be configured in this crate somehow, to avoid that issue.