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    SubjectRe: [PATCH] memory hotplug: Speed up add/remove when blocks are larger than PAGES_PER_SECTION
    On Wed, May 11, 2011 at 05:25:14PM +1000, Anton Blanchard wrote:
    >
    > On ppc64 the minimum memory section for hotplug is 16MB but most
    > recent machines have a memory block size of 256MB. This means
    > memory_block_change_state does 16 separate calls to
    > memory_section_action.
    >
    > This also means we call the notifiers 16 times and the hook
    > in the ehea network driver is quite costly. To offline one 256MB
    > region takes:
    >
    > # time echo offline > /sys/devices/system/memory/memory32/state
    > 7.9s
    >
    > This patch removes the loop and calls online_pages or
    > remove_memory once for the entire region and in doing so makes
    > the logic simpler since we don't have to back out if things fail
    > part way through.
    >
    > The same test to offline one region now takes:
    >
    > # time echo online > /sys/devices/system/memory/memory32/state
    > 0.67s
    >
    > Over 11 times faster.

    Very nice job, I'll queue this up for .40.

    thanks,

    greg k-h


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