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    Subject[PATCH 62 of 66] disable transparent hugepages by default on small systems
    From: Rik van Riel <>

    On small systems, the extra memory used by the anti-fragmentation
    memory reserve and simply because huge pages are smaller than large
    pages can easily outweigh the benefits of less TLB misses.

    In case of the crashdump kernel, OOMs have been observed due to
    the anti-fragmentation memory reserve taking up a large fraction
    of the crashdump image.

    This patch disables transparent hugepages on systems with less
    than 1GB of RAM, but the hugepage subsystem is fully initialized
    so administrators can enable THP through /sys if desired.

    v2: reduce the limit to 512MB

    Signed-off-by: Rik van Riel <>
    Acked-by: Avi Kiviti <>
    Signed-off-by: Andrea Arcangeli <>

    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -527,6 +527,14 @@ static int __init hugepage_init(void)
    goto out;

    + /*
    + * By default disable transparent hugepages on smaller systems,
    + * where the extra memory used could hurt more than TLB overhead
    + * is likely to save. The admin can still enable it through /sys.
    + */
    + if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
    + transparent_hugepage_flags = 0;


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      Last update: 2010-11-03 16:53    [W:0.032 / U:14.832 seconds]
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