Unimporting modules, memory leak?

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  • Antonio Arauzo Azofra

    #1

    Unimporting modules, memory leak?

    Hello everybody,

    Probably, this is being too demanding for Python, but it may be
    useful to unimport modules to work with dynamic code (though not the
    best, one example is [2]). In fact, it is supposed to be possible[1],
    but I have detected it usually leaks memory.

    When unimported in Linux, the simple C module attached (has no
    functions, just the structure) leaks two memory pages

    To see the test you can just put the files in a directory and:
    python setupmod1.py install --install-lib .
    python testMemory.py

    Its output follows. First, the memory used before import. Second memory
    used after the import. Third the number of references to that object is
    checked before using del. Finally the memory used after unimporting.

    -- Testing mod1 --
    Mem. used: 1242 (gc: 0 )
    Mem. used: 1244 (gc: 0 )
    Check refs (should be = 2): 2
    Mem. used: 1244 (gc: 0 )
    -- Testing bigModule --
    Mem. used: 1244 (gc: 0 )
    Mem. used: 2686 (gc: 0 )
    Check refs (should be = 2): 2
    Mem. used: 1244 (gc: 0 )
    -- Testing random --
    Mem. used: 1244 (gc: 0 )
    Mem. used: 1256 (gc: 0 )
    Check refs (should be = 2): 2
    Mem. used: 1256 (gc: 57 )

    Unimporting attached "bigmodule. py" there are no memory leaks.
    Unimporting python's random module it leaks some pages, but garbage
    collector admit it can not free them.

    If a module with the same name that the unimported module is imported,
    the pages are reused. While, if this same module is loaded with another
    name, they are not freed, and the program grows with each module
    imported/unimported

    Is this a Python bug? A Linux bug? Am i missing some way of freeing that
    memory used by C module?

    [1] http://mail.python.org/pipermail/pyt...ay/002669.html
    [2] http://ax5.com/antonio/orangesnns
    --
    Saludos,
    Antonio Arauzo Azofra

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