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    SubjectRe: [00/41] Large Blocksize Support V7 (adds memmap support)
    Andrea Arcangeli <> writes:

    > On Sat, Sep 15, 2007 at 02:14:42PM +0200, Goswin von Brederlow wrote:
    >> I keep coming back to the fact that movable objects should be moved
    >> out of the way for unmovable ones. Anything else just allows
    > That's incidentally exactly what the slab does, no need to reinvent
    > the wheel for that, it's an old problem and there's room for
    > optimization in the slab partial-reuse logic too. Just boost the order
    > 0 page size and use the slab to get the 4k chunks. The sgi/defrag
    > design is backwards.

    How does that help? Will slabs move objects around to combine two
    partially filled slabs into nearly full one? If not consider this:

    - You create a slab for 4k objects based on 64k compound pages.
    (first of all that wastes you a page already for the meta infos)
    - Something movable allocates a 14 4k page in there making the slab
    partially filled.
    - Something unmovable alloactes a 4k page making the slab mixed and
    - Repeat until out of memory.


    - Userspace allocates a lot of memory in those slabs.
    - Userspace frees one in every 15 4k chunks.
    - Userspace forks 1000 times causing an unmovable task structure to
    appear in 1000 slabs.

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      Last update: 2007-09-15 22:19    [W:0.021 / U:1.600 seconds]
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