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    SubjectRe: missing madvise functionality
    Date
    On Tuesday 03 April 2007, Ulrich Drepper wrote:
    > The problem is glibc has to work around kernel limitations.  If the
    > malloc implementation detects that a large chunk of previously allocated
    > memory is now free and unused it wants to return the memory to the
    > system.  What we currently have to do is this:
    >
    >   to free:      mmap(PROT_NONE) over the area
    >   to reuse:     mprotect(PROT_READ|PROT_WRITE)
    >
    > Yep, that's expensive, both operations need to get locks preventing
    > other threads from doing the same.

    I thought this is what the read_zero_pagealigned hack [1] was used
    for (read from /dev/zero replaces target pages with empty_zero_page).
    Now if read_zero_pagealigned does not solve _this_ scenario, is it
    good for anything else then?
    Can we simply kill that function as a misfeature and avoid future
    pain arising from it?

    Arnd <><

    [1] http://lkml.org/lkml/1997/1/16/49
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