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    SubjectRe: [patch] mmap-speedup-2.5.42-C3
    On Wed, Oct 16, 2002 at 10:03:52AM +0200, Ingo Molnar wrote:
    >
    > On 15 Oct 2002, Andi Kleen wrote:
    >
    > > When you oprofile KDE startup you notice that a lot of time is spent in
    > > get_unmapped_area too. The reason is that every KDE process links with
    > > 10-20 libraries and ends up with a 40-50 entry /proc/<pid>/maps.
    >
    > actually, library mappings alone should not cause a slowdown, since we
    > start the search at MAP_UNMAPPED_BASE and most library mappings are below
    > 1GB. But if those libraries use mmap()-ed anonymous RAM that has different
    > protections then the anonymous areas do not get merged and the scanning
    > overhead goes up.

    Libraries mapped by dynamic linker are mapped without MAP_FIXED and unless
    you use prelinking, with 0 virtual address, ie. they all end up above 1GB.
    And 99% of libraries uses different protections, for the read-only and
    read-write segment.

    Jakub
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