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    SubjectRe: [PATCH] mm: do not drain pagevecs for mlock
    Hi Kosaki,
    On 12/30/2011 06:07 PM, KOSAKI Motohiro wrote:
    >>> Because your test program is too artificial. 20sec/100000times =
    >>> 200usec. And your
    >>> program repeat mlock and munlock the exact same address. so, yes, if
    >>> lru_add_drain_all() is removed, it become near no-op. but it's
    >>> worthless comparision.
    >>> none of any practical program does such strange mlock usage.
    >> yes, I should say it is artificial. But mlock did cause the problem in
    >> our product system and perf shows that the mlock uses the system time
    >> much more than others. That's the reason we created this program to test
    >> whether mlock really sucks. And we compared the result with
    >> rhel5(2.6.18) which runs much much faster.
    >>
    >> And from the commit log you described, we can remove lru_add_drain_all
    >> safely here, so why add it? At least removing it makes mlock much faster
    >> compared to the vanilla kernel.
    >
    > If we remove it, we lose to a test way of mlock. "Memlocked" field of
    > /proc/meminfo
    > show inaccurate number very easily. So, if 200usec is no avoidable,
    > I'll ack you.
    > But I'm not convinced yet.
    Do you find something new for this?

    Thanks
    Tao


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