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    SubjectRe: /proc/*/statm, exactly what does "shared" mean?
    Hi all,

    Sorry for responding this email so late. I was busy with my trip.

    On Sat, 12 Feb 2005 15:42:15 +0000 (GMT), Hugh Dickins <> wrote:
    > On Sat, 12 Feb 2005, Richard F. Rebel wrote:
    > >
    > > That said, many mod_perl users are *VERY* interested in being able to
    > > detect and observe how "shared" our forked children are. Shared meaning
    > > private pages shared with children (copy on write). Is it even possible
    > > to do this in 2.6 kernels? If so, any pointers would be very helpful.
    > Not in any of the vanilla kernels.
    > Mauricio has a /proc/<pid>/smaps patch, in which he returns to looking
    > at every pte slot of every vma of the process as /proc/<pid>/statm did
    > in 2.4. I suggest you ask him offline for his latest version (the last
    > I saw did not include support for 2.6.11's pud level;
    I put the pud level on the last patch I sent to the linux-kernel list
    as suggested by Marcelo Tosatti.

    > and looped in an
    > inefficient way, repeatedly locating, mapping and unmapping the page
    > table for each pte slot - needs refactoring into pgd_range, pud_range,
    > pmd_range, pte_range levels like 2.4's statm).
    Well, for each vma it is checked how many pages are mapped to rss. So
    I have to check per page if it is allocated in physical memory. I know
    that this is a heavy function, but do you have any suggestion to
    improve this? What do you mean "needs refactoring into pgd_range,
    pud_range, pmd_range, pte_range levels like 2.4's statm"? Could you
    give more details, please?


    Mauricio Lin.
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