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    SubjectRe: [PATCH] vmscan: limit concurrent reclaimers in shrink_zone
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    On Fri, Dec 11, 2009 at 12:19 PM, Rik van Riel <riel@redhat.com> wrote:
    > On 12/10/2009 09:03 PM, Minchan Kim wrote:
    >
    >>> +The default value is 8.
    >>> +
    >>> +=============================================================
    >>
    >> I like this. but why do you select default value as constant 8?
    >> Do you have any reason?
    >>
    >> I think it would be better to select the number proportional to NR_CPU.
    >> ex) NR_CPU * 2 or something.
    >>
    >> Otherwise looks good to me.
    >
    > Pessimistically, I assume that the pageout code spends maybe
    > 10% of its time on locking (we have seen far, far worse than
    > this with thousands of processes in the pageout code).  That
    > means if we have more than 10 threads in the pageout code,
    > we could end up spending more time on locking and less doing
    > real work - slowing everybody down.

    Thanks for giving precious information to me. :

    We always have a question magic value with no comment.

    Actually I don't want to add another magic value without comment.
    so I would like to add the your good explanation in change log
    or as comment on code.

    >
    > I rounded it down to the closest power of 2 to come up with
    > an arbitrary number that looked safe :)
    >
    > However, this number is per zone - I imagine that really large
    > systems will have multiple memory zones, so they can run with
    > more than 8 processes in the pageout code simultaneously.
    >
    >> Reviewed-by: Minchan Kim<minchan.kim@gmail.com>
    >
    > Thank you.

    Thanks for quick reply. :)

    > --
    > All rights reversed.
    >



    --
    Kind regards,
    Minchan Kim
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