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    SubjectRe: WARNING: at mm/page-writeback.c:1990 __set_page_dirty_nobuffers+0x13a/0x170()
    > In changelog, Bartlomiej said.
    >
    > My particular test case (on a ARM EXYNOS4 device with 512 MiB, which means
    > 131072 standard 4KiB pages in 'Normal' zone) is to:
    >
    > - allocate 120000 pages for kernel's usage
    > - free every second page (60000 pages) of memory just allocated
    > - allocate and use 60000 pages from user space
    > - free remaining 60000 pages of kernel memory
    > (now we have fragmented memory occupied mostly by user space pages)
    > - try to allocate 100 order-9 (2048 KiB) pages for kernel's usage
    >
    > The results:
    > - with compaction disabled I get 11 successful allocations
    > - with compaction enabled - 14 successful allocations
    > - with this patch I'm able to get all 100 successful allocations
    >
    > I think above workload is really really artificial and theoretical so I didn't like
    > this patch but Mel seem to like it. :(
    >
    > Quote from Mel
    > " Ok, that is indeed an adverse workload that the current system will not
    > properly deal with. I think you are right to try fixing this but may need
    > a different approach that takes the cost out of the allocation/free path
    > and moves it the compaction path."
    >
    > We can correct this patch to work but at least need justification about it.
    > Do we really need this patch for such artificial workload?
    > what do you think?

    I'm ok to resubmit. But please change the thread.



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