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    Subject[QUICKLIST 0/4] Arch independent quicklists V2
    - Add sparch64 patch
    - Single i386 and x86_64 patch
    - Update attribution
    - Update justification
    - Update approvals
    - Earlier discussion of V1 was at

    This patchset introduces an arch independent framework to handle lists
    of recently used page table pages. It is necessary for x86_64 and
    i386 to avoid the special casing of SLUB because these two platforms
    use fields in the page_struct (page->index and page->private)
    that SLUB needs (and in fact SLAB also needs page-private if
    performing debugging!). There is also the tendency of arches to use
    page flags to mark page table pages. The slab also uses page flags.
    Separating page table page allocation into quicklists avoids the danger
    of conflicts and frees up page flags for SLUB and for the arch code.

    Page table pages have the characteristics that they are typically zero
    or in a known state when they are freed. This is usually the exactly
    same state as needed after allocation. So it makes sense to build a list
    of freed page table pages and then consume the pages already in use
    first. Those pages have already been initialized correctly (thus no
    need to zero them) and are likely already cached in such a way that
    the MMU can use them most effectively. Page table pages are used in
    a sparse way so zeroing them on allocation is not too useful.

    Such an implementation already exits for ia64. Howver, that implementation
    did not support constructors and destructors as needed by i386 / x86_64.
    It also only supported a single quicklist. The implementation here has
    constructor and destructor support as well as the ability for an arch to
    specify how many quicklists are needed.

    Quicklists are defined by an arch defining the necessary number
    of quicklists in arch/<arch>/Kconfig. F.e. i386 needs two and thus

    config NR_QUICK
    default 2

    If an arch has requested quicklist support then pages can be allocated
    from the quicklist (or from the page allocator if the quicklist is
    empty) via:

    quicklist_alloc(<quicklist-nr>, <gfpflags>, <constructor>)

    Page table pages can be freed using:

    quicklist_free(<quicklist-nr>, <destructor>, <page>)

    Pages must have a definite state after allocation and before
    they are freed. If no constructor is specified then pages
    will be zeroed on allocation and must be zeroed before they are

    If a constructor is used then the constructor will establish
    a definite page state. F.e. the i386 and x86_64 pgd constructors
    establish certain mappings.

    Constructors and destructors can also be used to track the pages.
    i386 and x86_64 use a list of pgds in order to be able to dynamically
    update standard mappings.

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      Last update: 2007-03-13 08:15    [W:0.023 / U:10.960 seconds]
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