• Jianguo Wu's avatar
    mm: fix-up zone present pages · 7f1290f2
    Jianguo Wu authored
    I think zone->present_pages indicates pages that buddy system can management,
    it should be:
    
    	zone->present_pages = spanned pages - absent pages - bootmem pages,
    
    but is now:
    	zone->present_pages = spanned pages - absent pages - memmap pages.
    
    spanned pages: total size, including holes.
    absent pages: holes.
    bootmem pages: pages used in system boot, managed by bootmem allocator.
    memmap pages: pages used by page structs.
    
    This may cause zone->present_pages less than it should be.  For example,
    numa node 1 has ZONE_NORMAL and ZONE_MOVABLE, it's memmap and other
    bootmem will be allocated from ZONE_MOVABLE, so ZONE_NORMAL's
    present_pages should be spanned pages - absent pages, but now it also
    minus memmap pages(free_area_init_core), which are actually allocated from
    ZONE_MOVABLE.  When offlining all memory of a zone, this will cause
    zone->present_pages less than 0, because present_pages is unsigned long
    type, it is actually a very large integer, it indirectly caused
    zone->watermark[WMARK_MIN] becomes a large
    integer(setup_per_zone_wmarks()), than cause totalreserve_pages become a
    large integer(calculate_totalreserve_pages()), and finally cause memory
    allocating failure when fork process(__vm_enough_memory()).
    
    [root@localhost ~]# dmesg
    -bash: fork: Cannot allocate memory
    
    I think the bug described in
    
      http://marc.info/?l=linux-mm&m=134502182714186&w=2
    
    is also caused by wrong zone present pages.
    
    This patch intends to fix-up zone->present_pages when memory are freed to
    buddy system on x86_64 and IA64 platforms.
    Signed-off-by: 's avatarJianguo Wu <wujianguo@huawei.com>
    Signed-off-by: 's avatarJiang Liu <jiang.liu@huawei.com>
    Reported-by: 's avatarPetr Tesarik <ptesarik@suse.cz>
    Tested-by: 's avatarPetr Tesarik <ptesarik@suse.cz>
    Cc: "Luck, Tony" <tony.luck@intel.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Cc: Yinghai Lu <yinghai@kernel.org>
    Cc: Minchan Kim <minchan.kim@gmail.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: David Rientjes <rientjes@google.com>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    7f1290f2
nobootmem.c 10.6 KB