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    mm, THP, swap: check whether THP can be split firstly · b8f593cd
    Huang Ying 提交于
    To swap out THP (Transparent Huage Page), before splitting the THP, the
    swap cluster will be allocated and the THP will be added into the swap
    cache.  But it is possible that the THP cannot be split, so that we must
    delete the THP from the swap cache and free the swap cluster.  To avoid
    that, in this patch, whether the THP can be split is checked firstly.
    The check can only be done racy, but it is good enough for most cases.
    
    With the patch, the swap out throughput improves 3.6% (from about
    4.16GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case
    with 8 processes.  The test is done on a Xeon E5 v3 system.  The swap
    device used is a RAM simulated PMEM (persistent memory) device.  To test
    the sequential swapping out, the test case creates 8 processes, which
    sequentially allocate and write to the anonymous pages until the RAM and
    part of the swap device is used up.
    
    Link: http://lkml.kernel.org/r/20170515112522.32457-5-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
    Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> [for can_split_huge_page()]
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Shaohua Li <shli@kernel.org>
    Cc: Tejun Heo <tj@kernel.org>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    b8f593cd
huge_memory.c 74.5 KB