[Python-Dev] this is what happens if you freeze all the modules required for startup

[Brett Cannon]

Because people keep bringing it up, below is the results of hacking up the
interpreter to include a sys.path entry for ./python35.zip instead of
hard-coding to /usr/lib/python35.zip and simply zipped up Lib/ recursively.
TL;DR, zipimport performance no longer measures up (probably because of
stat caching and such that importlib introduced).

### normal_startup ###

Min: 0.510211 -> 2.667958: 5.23x slower

Avg: 0.521073 -> 2.694876: 5.17x slower

Significant (t=-1129.54)

Stddev: 0.00478 -> 0.01274: 2.6681x larger


### startup_nosite ###

Min: 0.304090 -> 0.908059: 2.99x slower

Avg: 0.312374 -> 0.921807: 2.95x slower

Significant (t=-797.79)

Stddev: 0.00372 -> 0.00667: 1.7956x larger



-Brett

On Mon Apr 14 2014 at 5:51:23 PM, Brett Cannon <bcannon at gmail.com> wrote:

> It was realized during PyCon that since we are freezing importlib we could
> now consider freezing all the modules to cut out having to stat or read
> them from disk. So for day 1 of the sprints I I decided to hack up a
> proof-of-concept to see what kind of performance gain it would get.
>
> Freezing everything except encodings.__init__, os, and _sysconfigdata, it
> speeds up startup by 11% compared to default. Compared to 2.7 it shaves 14%
> from the slowdown (27% slower vs. 41% slower). The full results are at the
> end of the email.
>
> Now the question is whether the maintenance cost of having to rebuild
> Python for a select number of stdlib modules is enough to warrant putting
> in the effort to make this work. My guess is the best approach would be
> adding a Lib/_frozen directory where any modules that we treat like this
> would be kept to act as a reminder that you need to rebuild for them (I
> would probably move importlib/_boostrap.py as well to make this consistent).
>
> Thoughts?
>
>
> --------------------------------------
>
> default vs the freezing:
>
> ### normal_startup ###
>
> Min: 0.524812 -> 0.473339: 1.11x faster
>
> Avg: 0.534403 -> 0.481245: 1.11x faster
>
> Significant (t=61.80)
>
> Stddev: 0.00466 -> 0.00391: 1.1909x smaller
>
>
> ### startup_nosite ###
>
> Min: 0.307359 -> 0.291939: 1.05x faster
>
> Avg: 0.317667 -> 0.300156: 1.06x faster
>
> Significant (t=26.29)
>
> Stddev: 0.00543 -> 0.00385: 1.4099x smaller
>
> ---------
>
> 2.7 vs the freezing:
>
> ### normal_startup ###
>
> Min: 0.367571 -> 0.465264: 1.27x slower
>
> Avg: 0.374404 -> 0.476662: 1.27x slower
>
> Significant (t=-90.26)
>
> Stddev: 0.00313 -> 0.00738: 2.3603x larger
>
>
> ### startup_nosite ###
>
> Min: 0.164510 -> 0.290544: 1.77x slower
>
> Avg: 0.169833 -> 0.301109: 1.77x slower
>
> Significant (t=-286.30)
>
> Stddev: 0.00211 -> 0.00407: 1.9310x larger
>
> ---------
>
> As a baseline, 2.7 vs default:
>
> ### normal_startup ###
>
> Min: 0.368916 -> 0.521758: 1.41x slower
>
> Avg: 0.376784 -> 0.531883: 1.41x slower
>
> Significant (t=-172.82)
>
> Stddev: 0.00423 -> 0.00474: 1.1207x larger
>
>
> ### startup_nosite ###
>
> Min: 0.165156 -> 0.309090: 1.87x slower
>
> Avg: 0.171516 -> 0.319004: 1.86x slower
>
> Significant (t=-283.45)
>
> Stddev: 0.00334 -> 0.00399: 1.1948x larger
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20140417/98fbc7ff/attachment.html>