[Python-Dev] 2.3 startup speed? (original) (raw)

Jeremy Hylton jeremy@zope.com
11 Jul 2003 13:25:14 -0400

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On Thu, 2003-07-10 at 16:15, Aahz wrote:

What's the current status of the startup speed for Python 2.3? Did anyone ever check in fixes for that?

I did some more measurements of what I think are startup time and teardown time. I assume people who care about startup time for small scripts care about teardown time for small scripts, too, since it's time spent executing code. (You might consider it time wasted, since the process is exiting and it's mostly giving memory back to obmalloc <0.5 wink>.)

I measured the time it takes to execute two different scripts: python -c "pass" and python -c "import os; os._exit(0)". I believe the os._exit() script measures just startup time, because the process exits immediately without running Py_Finalize(). So I'll refer to two times "total" time and "startup" time for the two scripts.

I took the measurements after the warnings changes I made today.

Times reported here are the minimum of each real, user, and sys time over 10 runs of the script. This is on my RH 7.3 desktop. (Timing script attached.)

py kind real user sys (time in ms) 2.2 total 32 21 2 2.2 startup 29 14 4

2.3 total 53 33 6 2.3 startup 41 21 4

(I took the minimums of the individual component times, so they don't add up quite right.)

One thing to observe is that the teardown time (the difference between total and startup) is much larger in 2.3. It's 3ms in 2.2 and 12ms in 2.3. We added to extra GC collection phases to 2.3 teardown, so that isn't too surprising.

One thing I learned is that timings take from a build directory are quite different from timings taken after an install. The cost of loading up distutils is high.

Jeremy

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#! /usr/bin/env python

"""Simple script to time Python startup time"""

import os

def timeit1(stmt): """Return real, user, and sys from single execution.""" i, o, e = os.popen3('time %s -c "%s"' % (py, stmt)) buf = e.read() i.close() o.close() e.close() return parse_time(buf)

def timeit(stmt, iters=10): """Return the lowest real, user, and sys each from iters trials.""" L = [timeit1(stmt) for i in range(iters)] return map(min, zip(*L))

def parse_time(buf): real = None user = None sys = None for line in buf.split("\n"): if not line: continue kind, _t = line.split("\t") t = int(float(_t[2:-1]) * 1000) if kind == "real": real = t elif kind == "user": user = t elif kind == "sys": sys = t return real, user, sys

def main(argv): global py py = argv[0]

total = timeit("pass")
startup = timeit("import os; os._exit(0)")

print py
print "kind     real  user   sys  (time in ms)"
fmt = "%-8s %4s  %4s  %4s"
print fmt % ("total", total[0], total[1], total[2])
print fmt % ("startup", startup[0], startup[1], startup[2])

if name == "main": import sys main(sys.argv[1:])

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