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    SubjectRe: [rfc][patch] store-free path walking
    On Thu, Oct 08, 2009 at 09:39:30AM +0200, Nick Piggin wrote:
    > > My point (probably not very well written expressed)
    > > was that in a typical VFS operation there are hundreds
    > > of cache lines touched for various things (code, global, various
    > > objects, random stuff) and one more or less in the final dentry
    > > is not that big a difference in the global picture.
    > > (ok I realize final in this case means the elements in the path)
    > Yes I do know what you were getting at... Although I would
    > say dcache is still fairly significant. It's 3 cachelines
    > for every single path element we look up. Now I suspect it

    That's true, for deeply nested paths where the elements add up
    it's a concern. I was assuming that paths are not that deep, but that might
    be too optimistic.

    > Actually no, it does look relatively sane (I guess it doesn't
    > change that much), except it might actualy be a nice idea
    > to move d_iname up to about above d_lru, so we could actually
    > do path lookup in 2 cachelines per entry (or even 1 if we
    > they have very short names).
    > I will do a bit of profiling on the lookup code and see...

    Yes numbers would be great.

    -- -- Speaking for myself only.

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