Python Profiling

Date:2013-03-15
Speaker:Amjith Ramanujam

What is it?

  • This is nothing like racial profiling
  • All about measuring performance

cProfile

  • The jam, part of the standard library
  • python -m cProfile lcm.py
  • Dump to a .pstats file

GUI Profiler: RunSnakeRun

  • Makes pretty square maps of stuff
  • Sort by column, drill down, awesome.

Tips

  • Huge overhead
  • “Don’t run in production!”
  • Slow
  • Not realistic

Targeted Profiling

  • Critical functions

  • Start profiler, profile critical thing, stop profiler

  • from profile_func import profile_func:

    @profile_func
def lcm(arg1, arg2):
    # ...

  • You don’t want to affect your critical function!

  • Pros: less overhead, finer resolution

  • Cons: still slow, manual, littering code w/ decorators

New Relic

  • Targeted, hybrid profiling
  • Web apps only :/
  • (They don’t use cProfile)
  • Targeted profiling:
    • Web frameworks (django, etc)
    • View handlers
    • SQL calls
    • Monkey patch calls you care about

Hybrid profiling

  • Top-level function only
  • Timing data
  • Capture args
  • Waterfall diagram/graphing
  • Pros: fast, function args
  • Cons: semi-manual, limited instrumentation

Statistical Profiling

  • Non-deterministic
  • Kind of like overly-attached girlfriend
  • Interrupt, inquire, collate = OVERLY ATTACHED
    • Who are you with
    • Where are you
    • When are you coming home?
    • I miss you!
  • Interrupt (timer):
    • UNIX signals
    • Threads
  • Inquire (trace)
    • Stack frame of every thread
    • import sys, traceback
      • frames = sys._current_frames()
      • traceback.extract_stack(frame)
  • 3rd party libs
    • StatProf (UNIX signals, CLI)
    • PLOP (Unix Signals, D3 Call Graph), by DropBox
      • Size of the bubble indicates CPU time
    • New Relic (threads, GUI)

X-Ray Sessions

  • New Relic SECRET BETA (until now)
  • Deterministic
  • Targeted transactions (e.g. checkout page), count, gather, profile threads
  • Measure/graph the response & throughput
  • PROFILE ALL THE THINGS