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    SubjectRe: [RFC 2.6.11-rc2-mm2 0/7] mm: manual page migration -- overview II
    Andi Kleen wrote:

    >
    > How about you add the va_start, va_end but only accept them
    > when pid is 0 (= current process). Otherwise enforce with EINVAL
    > that they are both 0. This way you could map the
    > shared object into the batch manager, migrate it there, then
    > mark it somehow to not be migrated further, and then
    > migrate the anonymous pages using migrate_pages(pid, ...)
    >

    We'd have to use up a struct page flag (PG_MIGRATED?) to mark
    the page as migrated to keep the call to migrate_pages() for
    the anonymous pages from migrating the pages again. Then we'd
    have to have some way to clear PG_MIGRATED once all of the
    migrate_pages() calls are complete (we can't have the anonymous
    page migrate_pages() calls clear the flags, since the second
    such call would find the flag clear and remigrate the pages
    in the overlapping nodes case.)

    How about ignoring the va_start and va_end values unless
    either:

    pid == current->pid
    or current->euid == 0 /* we're root */

    I like the first check a bit better than checking for 0. Are
    there other system calls that follow that convention (e. g.
    pid = 0 implies current?)

    The second check lets a sufficiently responsible task manipulate
    other tasks. This task can choose to have the target tasks
    suspended before it starts fussing with them.

    > BTW it might be better to make va_end a size, just to be more
    > symmetric with mlock,madvise,mmap et.al.
    >

    Yes,.that's been pointed out to me before. Let's make it so.

    --
    Best Regards,
    Ray
    -----------------------------------------------
    Ray Bryant
    512-453-9679 (work) 512-507-7807 (cell)
    raybry@sgi.com raybry@austin.rr.com
    The box said: "Requires Windows 98 or better",
    so I installed Linux.
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