mapex: use more RAM, get rid of program startup lag

[GJones]

You know the story: you have a hulking workstation with a dozen GB of RAM, but you still have to wait for the hard disk to do its thing when you start a new program. This vexes me a bit, so I wrote a Python script to solve it:

Code: Select all

#!/usr/bin/env python2
import mmap, os, sys
import os.path

for paths in sys.argv:
    for root, dirs, files in os.walk(paths):
        for f in files:
            if (os.path.isfile(f) > 0) and (os.path.getsize(f) > 0):
                with open(f, "rb") as fd:
                    mmap.mmap(fd.fileno(), 0)

It would be invoked on a bunch of top level directories, like 'mapex.py /var /usr /opt'; maybe from a xinitrc or xprofile script. On the workstation I'm on now (Fedora 20, 4 GB RAM) it
- runs in 3-5 seconds
- causes the page cache to inflate by several hundred MB
- makes applications subsequently load in less than half the normal time

Needless to say it won't be very helpful on machines with < 1 GB of RAM.

(Also it's probably not idiomatic Python, but it gets the job done so whatever...)

Edit: slightly less stupid version below...

Code: Select all

#!/usr/bin/env python2
import mmap, os, os.path, sys

f_list = []
for arg in sys.argv:
  for root, dirs, files in os.walk(arg, followlinks=True):
    f_list.extend(files)

for f in f_list:
  if (os.path.exists(f) > 0) and (os.path.getsize(f) > 0) and (os.path.isfile(f) > 0):
    with open(f, "rb") as fd:
      mmap.mmap(fd.fileno(), 0)

Edit: yeah, let's *not* try for write access to files in /usr!