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    SubjectRe: [RFC][PATCH 00/26] sched/numa
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    On Mon, 2012-03-19 at 14:04 +0100, Andrea Arcangeli wrote:

    > About the cost of the actual pagetable scanner, you're not being
    > rational about it. You should measure it for once, take khugepaged
    > make it scan 1G of memory per millisecond and measure the cost.

    Death by a thousand cuts..

    > You keep complaining about the unaccountability of the pagetable
    > scanners in terms of process load, and that's a red herring as far as
    > I can tell. The irqs and ksoftirqd load in a busy server, is likely
    > much higher than whatever happens at the pagetable scanner level (sure
    > thing for khugepaged and by an huge order of magnitude so).

    Who says I agree with ksoftirqd? I would love to get rid of all things
    softirq. And I also think workqueues are over-/ab-used.

    > I don't
    > think this is a relevant concern anyway because the pagetable scanners
    > go over all memory in a equal amount so the cost would be evenly
    > distributed for all processes over time (the same cannot be said about
    > the irqs and ksoftrqid that will benefit only a few processes doing
    > I/O).

    So what about the case where all I do is compile kernels and we already
    have near perfect locality because everything is short running? You're
    still scanning that memory, and I get no benefit.


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