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    SubjectRe: [QUICKLIST 1/4] Quicklists for page table pages V5
    On Tue, 2007-04-10 at 21:04 -0700, Christoph Lameter wrote:
    > On Tue, 10 Apr 2007, Benjamin Herrenschmidt wrote:
    > > On Mon, 2007-04-09 at 11:25 -0700, Christoph Lameter wrote:
    > >
    > > > Quicklists for page table pages V5
    > >
    > > Looks interesting, but unfortunately not very useful at this point for
    > > powerpc unless you remove the assumption that quicklists contain
    > > pages...
    > Then quicklists wont be as simple anymore.
    > > On powerpc, we currently use kmem cache slabs (though that isn't
    > > terribly node friendly) whose sizes depend on the page size.
    > >
    > > For a 4K page size kernel, we have 4 level page tables and use 2 caches,
    > > PTE and PGD pages are 4K (thus are PAGE_SIZE'd), and PMD & PUD are 1K.
    > PTE and PGD could be run via quicklists? With PTEs you cover the most
    > common case. Quicklists using PGDs will allow to optimize using
    > preconstructed pages.
    > Its probably best to keep the slabs for the 1K pages.
    > > For a 64K page size kernel, we have 3 level page tables and we use 3
    > > caches: a PGD pages are 128 bytes (yeah, not big heh...), our pmd
    > > pages are 32K (half a page) and PTE pages are PAGE_SIZE (64K).
    > Ok so use quicklists for the PTEs and slab for the rest? A PGD of only 128
    > bytes? Stuff one at the end of the mm_struct or the task struct? That way
    > you can avoid allocation overhead.

    Yeah, maybe... I need to think about it a bit more. I might be able to
    make the PMD a full page too.


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