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    SubjectRe: test13-pre5
    On Thu, Dec 28, 2000 at 12:59:22PM -0800, Linus Torvalds wrote:
    > - we absolutely do _not_ want to make "struct page" bigger. We can't
    > afford to just throw away another 8 bytes per page on adding a new list
    > structure, I feel. Even if this would be the simplest solution.


    The current 2.4 struct page could be already shortened a lot, saving a lot
    of cache.
    (first number for 32bit, second for 64bit)

    - Do not compile virtual in when the kernel does not support highmem
    (saves 4/8 bytes)
    - Instead of having a zone pointer mask use a 8 or 16 byte index into a
    zone table. On a modern CPU it is much cheaper to do the and/shifts than
    to do even a single cache miss during page aging. On a lot of systems
    that zone index could be hardcoded to 0 anyways, giving better code.
    - Instead of using 4/8 bytes for the age use only 16bit (FreeBSD which
    has the same swapping algorithm even only uses 8bit)
    - Remove the waitqueue debugging (obvious @)
    - flags can be __u32 on 64bit hosts, sharing 64bit with something that
    is tolerant to async updates (e.g. the zone table index or the index)
    - index could be probably u32 instead of unsigned long, saving 4 bytes
    on i386

    Would you consider patches for any of these points?


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