contrib/memory.py

shelve: remove useless and incorrect code paths for file access

This patch removes code paths in "shelvedfile.opener()", because:

    - explicit "vfs.mkdir()" invocation is useless

      "vfs.__call__()" for modes other than "read" creates parent
      directory of target file automatically by "util.ensuredirs()".

    - mode checking in "except IOError" code path is useless

      ENOENT occurs only for "read" mode, because target file is
      created forcibly for other modes.

    - there is no explicit "return" statement in the code path for
      "except IOError" if "mode[0] in 'wa'"

      this is incorrect, because None may be returnd unexpectedly,
      even though it seems the EEXIST case in the directory creation
      race for ".hg/shelved" and is very rare.

      this directory creation race is also treated in
      "util.ensuredirs()".

# memory.py - track memory usage
#
# Copyright 2009 Matt Mackall <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''helper extension to measure memory usage

Reads current and peak memory usage from ``/proc/self/status`` and
prints it to ``stderr`` on exit.
'''

import atexit

def memusage(ui):
    """Report memory usage of the current process."""
    status = None
    result = {'peak': 0, 'rss': 0}
    try:
        # This will only work on systems with a /proc file system
        # (like Linux).
        status = open('/proc/self/status', 'r')
        for line in status:
            parts = line.split()
            key = parts[0][2:-1].lower()
            if key in result:
                result[key] = int(parts[1])
    finally:
        if status is not None:
            status.close()
    ui.write_err(", ".join(["%s: %.1f MiB" % (key, value / 1024.0)
                            for key, value in result.iteritems()]) + "\n")

def extsetup(ui):
    atexit.register(memusage, ui)