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    SubjectRe: [PATCH 0/5] mm: rework sys_move_pages() to avoid vmalloc and reduce the overhead
    By the way, this patchset replaces
    mm-use-a-radix-tree-to-make-do_move_pages-complexity-linear-checkpatch-fixes
    (currently in -mm).

    Brice



    Brice Goglin wrote:
    > Hello,
    >
    > Here's the first patchset reworking sys_move_pages() as discussed earlier.
    > It removes the possibly large vmalloc by using multiple chunks when migrating
    > large buffers. It also dramatically increases the throughput for large buffers
    > since the lookup in new_page_node() is now limited to a single chunk, causing
    > the quadratic complexity to have a much slower impact. There is no need to use
    > any radix-tree-like structure to improve this lookup.
    >
    > sys_move_pages() duration on a 4-quadcore-opteron 2347HE (1.9Gz), migrating
    > between nodes #2 and #3:
    > length move_pages (us) move_pages+patch (us)
    > 4kB 126 98
    > 40kB 198 168
    > 400kB 963 937
    > 4MB 12503 11930
    > 40MB 246867 11848
    >
    > Patches #1 and #4 are the important ones:
    > 1) stop returning -ENOENT from sys_move_pages() if nothing got migrated
    > 2) don't vmalloc a huge page_to_node array for do_pages_stat()
    > 3) extract do_pages_move() out of sys_move_pages()
    > 4) rework do_pages_move() to work on page_sized chunks
    > 5) move_pages: no need to set pp->page to ZERO_PAGE(0) by default
    >
    > thanks,
    > Brice
    >
    >
    >
    >



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