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    Subjectmm - a page-centric kswapd
    Greetings all!

    I've just managed to get a preliminary version of my memory management
    changes working, and it seems to be performing quite well in my tests -
    it's the first time I've been able to run X on my 8 meg 486 w/nfs
    mounted /usr without crashing or being insanely slow. This version only
    works on i386 machines because I haven't made the appropriate changes to
    the various asm-*/pgtable.h.

    In order to provide a means to find ptes mapped to a given page, all page
    tables are now allocated with an order of 1. The second page provides a
    single pointer to the next pte on the list of a given page. For
    debugging purposes, a circular singly linked list is used, although it is
    my intention for the list not to be circular. This is in contrast to
    Mark Hemment's idea of using per-page pools that hold pointers to the
    ptes mapped to a page (which may very well be better =).

    In any case, this mechanism can be easily changed as pte linking is done
    through the functions in asm/pgtable.h:
    pte_link(pte_t *pte_p, unsigned long page)
    pte_unlink(pte_t *pte_p, unsigned long page)

    There are a couple of additional primatives defined in pgtable.h:
    pmd_t *pte_getpmd(pte_t *pte_p)
    pgd_t *pmd_getpgd(pmd_t *pmd_p)
    struct mm_struct *pgd_getmm(pgd_t *pgd_p)

    This allows one to find the mm_struct a given pte belows to....
    nescessary if you want to find the vm_operations to apply to a given page
    (see the new mm/vmscan.c)

    The code in vmscan.c now scans pages using a single handed clock
    algorithm (as mm/filemap.c:shrink_mmap did) - yeah it's pretty bad, but
    I've been trying to make the basic code stable (it now seems to be - all
    the pte_links in the right places ;). The behaviour wrt shared pages is
    very different from the old kswapd - such pages only get touched once for
    all mappings as opposed to the many times by the old code. This means
    shared pages do *not* have an advantage over non-shared pages, making
    kswapd able to free pages much faster.

    The willdo list:
    - steal_specific_page
    -> use to build free pages of orders approaching max
    - try_to_flip_page_to(dst_page, priv_page)
    - kswapd using active/inactive/freeable queues
    - smp friendly page fault handler

    The patch is located at
    It needs to be applied with patch -S -p2 -d linux_dir/ ... your favourite
    options. Any comments/feedback/suggestions would be appreciated, as
    that's what this is all about!


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