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

[Guido van Rossum]

I'm sorry to keep asking dumb questions, but your description didn't job my
understanding of what you are comparing here. What is slower than what?


On Thu, Apr 17, 2014 at 11:47 AM, Brett Cannon <bcannon at gmail.com> wrote:

> 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
>>
>
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-- 
--Guido van Rossum (python.org/~guido)
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