Messages in this thread | | | Subject | Re: [RFC][PATCH 00/26] sched/numa | From | Peter Zijlstra <> | Date | Mon, 19 Mar 2012 14:26:34 +0100 |
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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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