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

Nick Coghlan ncoghlan at gmail.com
Thu Jul 20 22:52:11 EDT 2017

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 cache_from_source" "cache = cache_from_source(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

More information about the Python-Dev mailing list