JIT Compiler Logs

JitLog is a PyPy logging facility that outputs information about compiler internals. It was built primarily for the following use cases:

  • Understand JIT internals and be able to browse emitted code (both IR operations and machine code)
  • Track down speed issues
  • Help bug reporting

This version is now integrated within the webservice vmprof.com and can be used free of charge.


The following commands show example usages:

# upload both vmprof & jitlog profiles
pypy -m vmprof --web --jitlog <program.py> <arguments>

# upload only a jitlog profile
pypy -m jitlog --web <program.py> <arguments>

# upload a jitlog when your program segfaults/crashes
$ pypy -m jitlog -o /tmp/file.log <program.py> <arguments>
$ pypy -m jitlog --upload /tmp/file.log