[Python-Dev] Python startup time (original) (raw)

Cesare Di Mauro cesare.di.mauro at gmail.com
Fri Jul 21 01:30:06 EDT 2017

2017-07-21 4:52 GMT+02:00 Nick Coghlan <ncoghlan at gmail.com>:

On 21 July 2017 at 12:44, Nick Coghlan <ncoghlan at gmail.com> wrote: > We can separately measure the cost of unmarshalling the code object: > > $ python3 -m perf timeit -s "import typing; from marshal import loads; from > importlib.util import cachefromsource; cache = > cachefromsource(typing.file); data = open(cache, 'rb').read()[12:]" > "loads(data)" > ..................... > Mean +- std dev: 286 us +- 4 us

Slight adjustment here, as the cost of locating the cached bytecode and reading it from disk should really be accounted for in each iteration: $ python3 -m perf timeit -s "import typing; from marshal import loads; from importlib.util import cachefromsource" "cache = cachefromsource(typing.spec.origin); data = open(cache, 'rb').read()[12:]; loads(data)" ..................... Mean +- std dev: 337 us +- 8 us That will have a bigger impact when loading from spinning disk or a network drive, but it's fairly negligible when loading from a local SSD or an already primed filesystem cache. Cheers, Nick. -- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia Thanks for your tests, Nick. It's quite evident that the marshal code cannot improve the situation, so I regret from my proposal.

I took a look at the typing module, and there are some small things that can be optimized, but it'll not change the overall situation unfortunately.

Code execution can be improved. :) However, it requires a massive amount of time experimenting...

Bests, Cesare

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