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    SubjectRe: [PATCH] add "VmUsers: N" to /proc/$PID/status
    On Thursday 16 July 2009 21:46, wrote:
    > On Wed, 15 Jul 2009 03:22:18 +0200, Denys Vlasenko said:
    > > It can be nice to know how many such CLONE_VM'ed processes
    > > share VM with given /proc/PID. Then it would be possible to do
    > > more accurate accounting of memory usage. Say, by dividing
    > > all memory usage numbers of this process by this number.
    > Process A clones a process A1. Process B clones a process B1. Now
    > all 4 of them have 'VmUsers: 2' on them, but there's no clean way to tell
    > whether A1 or B1 is the one sharing with A, or with B.
    > The patch is probably sufficient if all you want is some N to divide by, but
    > not if you care *which* processes are sharing how much.

    You are right. There is more: the truly accurate accounting
    needs to be per page. Like /proc/$PID/smaps
    and /proc/$PID/pagemap. (However, I am not sure you can
    relize that two processes share a VM by looking
    at these files either)

    I do not aim to solve _that_ problem with my patch.

    I, indeed, want to have just an N I can divide RSS/VSZ/etc by,
    to get, say, top display which do not mislead user
    into thinking that he has 3 processes with 100 megabyte RSS
    when in reality he has 3 processes sharing a single VM
    with 100 meg RSS.

    This will still not be completely accurate due to per-page
    sharing and such, but it will be more accurate
    than what we have now.

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