pyforkexec

WARNING: Read the warning section before you use this program.

pyforkexec is a program to speed up the execution of a user script. it optimizes the execution with the observation that, many user scripts can be split into 2 sections: the init section and the run section:

the init section is responsible for importing libraries, creating necessary data structures and doing other kinds of initialization. once the initialization is done, the init section is no longer needed.
the run section is responsible for the concrete job which utilizes the libraries imported and the data structures created in the init section.

typically, the init section needs to be run only once, while the run section may be run multiple times which all share the same context created by the init section. therefore, if the init section takes a long time, then it's better to run it once and cache the context for the following run sections. in this way, the run section no longer suffers the overhead from the init section.

the implementation uses a client-server architecture in which communication is done through a unix domain socket. the user runs a script using the client. but instead of running the script directly, the client actually sends the script to the server where it is actually run in a forked python vm. then the result is sent back via the same socket and fed into stdout and stderr of the client.

example

let's say we want to test if a str matches a regex.

import os
import re
import setuptools
import sys
pattern = re.compile('he.*ld')
print(pattern.match("helloworld"))

in my test, running this program directly takes about 300ms on a x86_64 linux box:

# time python3 -c "$(cat examples/helloworld.py)"
<_sre.SRE_Match object; span=(0, 10), match='helloworld'>

real    0m0.300s
user    0m0.271s
sys     0m0.028s

note that this program can be split into:

init section:

import os
import re
import setuptools
import sys
pattern = re.compile('he.*ld')

run section:
```
print(pattern.match("helloworld"))
```

with pyforkexec, we can run it as:

server:

# python3 server.py "$(cat examples/helloworld-init.py)"

client:

# time python3 client.py "$(cat examples/helloworld-run.py)"
<_sre.SRE_Match object; span=(0, 10), match='helloworld'>

real    0m0.048s
user    0m0.038s
sys     0m0.007s

the execution time is reduced from 300ms to less than 50ms.

some people might ask why one has to import os, sys and setuptools for a regex match. the answer is no we don't need those modules for a regex match. in this simple example, they are fictional and simply used to demonstrate what kind of problem pyforkexec can solve. however, this does not mean pyforkexec itself is fictional. in real applications, the above situation can happen, for example, when you need to use a library but have no control over its initialization, or when your project is still under heavy development and optimizing these details only has ephemeral effect and would negatively affect your development speed.

limitation

currently, pyforkexec is in very early stage. we are not quite sure what is right way to go next. and it has some limitations right now.

to give some examples of what should work:

print("helloworld")
print("total: {}".format(2 + 3))
import re;m = re.match("\d+", "123");print(m)

to give some examples of what won't work:

import os;print(os.path.abspath("."))

returns server dir instead of client dir.
import os;print(os.environ["foo"])

returns server env instead of client env.
import sys;print(sys.argv[3])

no command-line arguments yet.
a = input("name:")

no stdin yet.

it doesn't seem very difficult to resolve the above limitations, but it's hard to make sure those resolutions are the proper way of handling them and there aren't issues that are left out. therefore we prefer some discussions to show the direction before we actually evolve this project. interested readers can consult related threads on the python-dev and python-ideas mailing lists.

warning

pyforkexec uses exec() which can run almost any statements, and if used carelessly, can harm and even totally destroy your system. double check every line of the program and understand what's happending before you use it. the author assumes no warranty or liability at all for any kind of damage the program may cause.

license

The source code is licensed under the GNU General Public License v3.0.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

cykerway/pyforkexec

pyforkexec

example

limitation

warning

license