Empty output, + ERROR: No stack counts found

[blueberry]

Hi. Thank you for bringing attention to async-profiler, and for creating this package.

I've tried running an example you've provided on the homepage and the introductory blog post, and, while the package seems to work, the resulting /tmp/clj-async-profiler/... txt files are empty. The SVG file that prof/stop returns does not exist on disk.

The only complaint from (clj-)async-profiler is an error message printed in the repl (probably to err by the native binary itself) that says "ERROR: No stack counts found".

My system is a recent Arch Linux, OpenJDK 8, clj-async-profiler 0.1.3.

Any hints?

[alexander-yakushev]

Hello Dragan, can you please tell which build tool/runner you are using (Lein, boot, clj) and which version of it?

[blueberry]

Leiningen 2.8.1 on Java 1.8.0_162 OpenJDK 64-Bit Server VM

[alexander-yakushev]

I've just double-checked, it works for me on Ubuntu and Lein 2.8.1.

I assume you are running an x86_64 system?

[blueberry]

Yes.

A couple of things that I'm not completely sure about:

1. Is there anything additional to adding clj-async-profiler to the leiningen project that I should do?
2. How do I check if I have debug symbols enabled for the JVM? Could this be the source of the problem?

[alexander-yakushev]

Debug symbols shouldn't cause a problem here. And there is no additional config, really.

Let's do it once more step by step.

1. lein new ap-test.
2. Edit project.clj, add [com.clojure-goes-fast/clj-async-profiler "0.1.3"] to dependencies.
3. lein repl
4. (require '[clj-async-profiler.core :as p])
5. (p/profile-for 10 {})
6. After 10 seconds, two files should be present in /tmp/clj-async-profiler/results/.

ERROR: No stack counts found is reported by flamegraph generation script when it sees an empty file. Is that message shown again?

[blueberry]

I assume step 3 is lein repl instead of lein run. When I do this in vanilla terminal, I get a dozen of:

perf_event_open failed: Permission denied

printouts rigth after step 5.

The txt files in results are empty. No svg files are there.

[alexander-yakushev]

Are you doing this inside a Docker container, by chance?

[blueberry]

No. I'm doing it in vanilla desktop arch linux with x server and x monad, without Gnome or KDE or anything, with a normal account that has no exotic restrictions. All usual C development tools are recent, and I do lots of development on this machine...

[alexander-yakushev]

By Googling this message I found that newer Linux kernels have perf_event_paranoid set to 2 instead of 1, which restricts doing any kernel profiling from userspace.

Please, try doing echo 1 | sudo tee /proc/sys/kernel/perf_event_paranoid and try the profiler again.

[blueberry]

That didn't help.

Interestingly, running it as sudo lein repl works!

[alexander-yakushev]

Has the /proc/sys/kernel/perf_event_paranoid file changed? Does cat /proc/sys/kernel/perf_event_paranoid prints 1?

Can you also try setting it to 0?

[blueberry]

No, it prints 2. It seems that it's not being set by the command you suggested.

[alexander-yakushev]

I made a mistake initially:

echo 1 | sudo tee /proc/sys/kernel/perf_event_paranoid

[blueberry]

Works like a charm now! Many thanks!