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    SubjectRe: [RFC 1/4] hashtable: introduce a small and naive hashtable
    On Thu, Aug 2, 2012 at 1:25 PM, Josh Triplett <josh@joshtriplett.org> wrote:
    >
    > Sorry, I should clarify what I meant: you'll have a total of one extra
    > indirection, not two.

    Yes. But the hash table address generation is noticeably bigger and
    slower due to the non-fixed size too.

    In general, you can basically think of a dynamic hash table as always
    having one extra entry in the hash chains. Sure, the base address
    *may* cache well, but on the other hand, a smaller static hash table
    caches better than a big one, so you lose some and you win some.
    According to my numbers, you win a lot more than you lose.

    > Does your two-level dcache handle eviction?
    >
    > Mind posting the WIP patches?

    Attached. It's against an older kernel, but I suspect it still applies
    cleanly. The patch is certainly simple, but note the warning (you can
    *run* it, though - the race is almost entirely theoretical, so you can
    get numbers without ever seeing it)

    Linus
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