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    SubjectRe: [rfc] increase struct page size?!
    On Fri, May 18, 2007 at 12:19:05AM -0700, Andrew Morton wrote:
    > On Fri, 18 May 2007 06:08:54 +0200 Nick Piggin <npiggin@suse.de> wrote:
    >
    > > Many batch operations on struct page are completely random,
    >
    > But they shouldn't be: we should aim to place physically contiguous pages
    > into logically contiguous pagecache slots, for all the reasons we
    > discussed.

    For big IO batch operations, pagecache would be more likely to be
    physically contiguous, as would LRU, I suppose.

    I'm more thinking of operations where things get reclaimed over time,
    touched or dirtied in slightly different orderings, interleaved with
    other allocations, etc.


    > If/when that happens, there will be a *lot* of locality of reference
    > against the pageframes in a lot of important codepaths.

    And when it doesn't happen, we eat 75% more cache misses. And for that
    matter we eat 75% more cache misses for non-batch operations like
    allocating or freeing a page by slab, for example.

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