On Fri, Dec 10, 2021 at 09:04:25AM +0100, Peter Zijlstra wrote:

On Thu, Dec 09, 2021 at 09:04:25PM +0100, Jiri Olsa wrote:

quoted

hi,
after migrating to fedora 35 I found perf record hanging on exit
and it's because fedora 35 sets DEBUGINFOD_URLS that triggers
debuginfod query which might take long time to process.

I discussed this briefly with Frank and I'm sending the change
to disable debuginfod by default in perf record.

Frank had other idea we could discuss here to fork or just spawn
"/usr/bin/debuginfod-find ...." into background after perf record.

Perhaps there are other ways as well, hence this is RFC ;-)

thanks,
jirka


---
Fedora 35 sets by default DEBUGINFOD_URLS, which might lead
to unexpected stalls in perf record exit path, when we try
to cache profiled binaries.

  # DEBUGINFOD_PROGRESS=1 ./perf record -a
  ^C[ perf record: Woken up 1 times to write data ]
  Downloading from https://debuginfod.fedoraproject.org/ 447069
  Downloading from https://debuginfod.fedoraproject.org/ 1502175
  Downloading \^Z

Disabling DEBUGINFOD_URLS by default in perf record and adding
debuginfod option and .perfconfig variable support to enable id.

  Default without debuginfo processing:
  # perf record -a

  Using system debuginfod setup:
  # perf record -a --debuginfod

  Using custom debuginfd url:
  # perf record -a --debuginfod='https://evenbetterdebuginfodserver.krava'

Adding single perf_debuginfod_setup function and using
it also in perf buildid-cache command.

I'm still running with --no-buildid --no-buildid-cache or something like
that by default. As long as that remains working I'm good.

you're good ;-) that will bypass the problem completely

jirka