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    SubjectRe: [RFC] [PATCH] virtual memmap on sparsemem v3 [0/4] introduction
    On Sun, 10 Dec 2006 14:47:30 -0500
    "Bob Picco" <bob.picco@hp.com> wrote:
    > > Intro:
    > > When using SPARSEMEM, pfn_to_page()/page_to_pfn() accesses global big table
    > > of mem_section. if SPARSEMEM_EXTREME, this is 2-level table lookup.
    > Did you gather any performance numbers comparing
    > VIRTUAL_MEM_MAP+SPARSEMEM to SPARSEMEM+EXTREME? I did some quick but
    > inconclusive (small machine) ones when you first posted. There was
    > perhaps a slight degradation in VIRTUAL_MEM_MAP+SPARSEMEM.
    >
    No, I didn't. I'll do when I have a chance to do it. I hope that this won't
    be merged until someone shows the benefit by data.
    (I think this verion is better than the first one but..)

    IIRC, DISCONTIGMEM + VIRTUAL_MEM_MAP shows a bit better performance than
    SPARSEMEM_EXTREME. What I expect is to archive VIRTUAL_MEM_MAP performance
    with SPARSEMEM.

    Now, we still have chance to optimization.
    - optimize pfn_valid. (I'll post this. mem_section[] will be never accessed
    in runtime by this.)
    - use large-sized-page (no concrete idea, maybe to modify map/unmap func
    will work enough.)

    Thanks,
    -Kame

    -
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