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    SubjectRe: [PATCH] Document huge memory/cache overhead of memory controller in Kconfig
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    On Wednesday 20 February 2008 23:52, Balbir Singh wrote:
    > Andi Kleen wrote:
    > > Document huge memory/cache overhead of memory controller in Kconfig
    > >
    > > I was a little surprised that 2.6.25-rc* increased struct page for the
    > > memory controller. At least on many x86-64 machines it will not fit into
    > > a single cache line now anymore and also costs considerable amounts of
    > > RAM.
    >
    > The size of struct page earlier was 56 bytes on x86_64 and with 64 bytes it
    > won't fit into the cacheline anymore? Please also look at
    > http://lwn.net/Articles/234974/

    BTW. We'll probably want to increase the width of some counters
    in struct page at some point for 64-bit, so then it really will
    go over with the memory controller!

    Actually, an external data structure is a pretty good idea. We
    could probably do it easily with a radix tree (pfn->memory
    controller). And that might be a better option for distros.



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