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    SubjectRe: [PATCH] memcg: use do_div to divide s64 in 32 bit machine.
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    On Sun, Nov 7, 2010 at 2:19 AM, Greg Thelen <gthelen@google.com> wrote:
    > On Fri, Nov 5, 2010 at 6:03 PM,  <hannes@cmpxchg.org> wrote:
    >> On Sat, Nov 06, 2010 at 01:08:53AM +0900, Minchan Kim wrote:
    >>> Use do_div to divide s64 value. Otherwise, build would be failed
    >>> like Dave Young reported.
    >>
    >> I thought about that too, but then I asked myself why you would want
    >> to represent a number of pages as signed 64bit type, even on 32 bit?
    >
    > I think the reason that 64 byte type is used for page count in
    > memcontrol.c is because the low level res_counter primitives operate
    > on 64 bit counters, even on 32 bit machines.
    >
    >> Isn't the much better fix to get the types right instead?
    >>
    >
    > I agree that consistent types between mem_cgroup_dirty_info() and
    > global_dirty_info() is important.  There seems to be a lot of usage of
    > s64 for page counts in memcontrol.c, which I think is due to the
    > res_counter types.  I think these s64 be switched to unsigned long
    > rather to be consistent with the rest of mm code.  It looks like this
    > will be a clean patch, except for the lowest level where
    > res_counter_read_u64() is used, where some casting may be needed.
    >
    > I'll post a patch for that change.
    >

    Agree. I don't mind it.
    Thanks, Hannes and Greg.



    --
    Kind regards,
    Minchan Kim
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