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    SubjectRe: [PATCH] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous
    On Wed, Jun 01, 2011 at 01:57:47AM +0100, Mel Gorman wrote:
    > On Tue, May 31, 2011 at 04:14:02PM +0200, Andrea Arcangeli wrote:
    > > On Tue, May 31, 2011 at 10:33:40PM +0900, Minchan Kim wrote:
    > > > I checked them before sending patch but I got failed to find strange things. :(
    > >
    > > My review also doesn't show other bugs in migrate_pages callers like
    > > that one.
    > >
    > > > Now I am checking the page's SwapBacked flag can be changed
    > > > between before and after of migrate_pages so accounting of NR_ISOLATED_XX can
    > > > make mistake. I am approaching the failure, too. Hmm.
    > >
    > > When I checked that, I noticed the ClearPageSwapBacked in swapcache if
    > > radix insertion fails, but that happens before adding the page in the
    > > LRU so it shouldn't have a chance to be isolated.
    > >
    >
    > After hammering three machines for several hours, I managed to trigger
    > this once on x86 !CONFIG_SMP CONFIG_PREEMPT HIGHMEM4G (so no PAE)
    > and caught the following trace.
    >

    Umm, HIGHMEM4G implies a two-level pagetable layout so where are
    things like _PAGE_BIT_SPLITTING being set when THP is enabled?

    --
    Mel Gorman
    SUSE Labs


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