• Mel Gorman's avatar
    Choose pages from the per-cpu list based on migration type · 535131e6
    Mel Gorman authored
    
    
    The freelists for each migrate type can slowly become polluted due to the
    per-cpu list.  Consider what happens when the following happens
    
    1. A 2^(MAX_ORDER-1) list is reserved for __GFP_MOVABLE pages
    2. An order-0 page is allocated from the newly reserved block
    3. The page is freed and placed on the per-cpu list
    4. alloc_page() is called with GFP_KERNEL as the gfp_mask
    5. The per-cpu list is used to satisfy the allocation
    
    This results in a kernel page is in the middle of a migratable region. This
    patch prevents this leak occuring by storing the MIGRATE_ type of the page in
    page->private. On allocate, a page will only be returned of the desired type,
    else more pages will be allocated. This may temporarily allow a per-cpu list
    to go over the pcp->high limit but it'll be corrected on the next free. Care
    is taken to preserve the hotness of pages recently freed.
    
    The additional code is not measurably slower for the workloads we've tested.
    Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    535131e6
page_alloc.c 115 KB