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    Subject[PATCH v8 5/6] ksm: update the calculation of KSM profit
    Date
    From: xu xin <xu.xin16@zte.com.cn>

    When use_zero_pages is enabled, the calculation of ksm profit is not
    correct because ksm zero pages is not counted in. So update the
    calculation of KSM profit including the documentation.

    Signed-off-by: xu xin <xu.xin16@zte.com.cn>
    Cc: Xiaokai Ran <ran.xiaokai@zte.com.cn>
    Cc: Yang Yang <yang.yang29@zte.com.cn>
    Cc: Jiang Xuexin <jiang.xuexin@zte.com.cn>
    Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
    Cc: David Hildenbrand <david@redhat.com>
    ---
    Documentation/admin-guide/mm/ksm.rst | 18 +++++++++++-------
    mm/ksm.c | 2 +-
    2 files changed, 12 insertions(+), 8 deletions(-)

    diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
    index 019dc40a0d3c..dde7c152f0ae 100644
    --- a/Documentation/admin-guide/mm/ksm.rst
    +++ b/Documentation/admin-guide/mm/ksm.rst
    @@ -204,21 +204,25 @@ several times, which are unprofitable memory consumed.
    1) How to determine whether KSM save memory or consume memory in system-wide
    range? Here is a simple approximate calculation for reference::

    - general_profit =~ pages_sharing * sizeof(page) - (all_rmap_items) *
    + general_profit =~ ksm_saved_pages * sizeof(page) - (all_rmap_items) *
    sizeof(rmap_item);

    - where all_rmap_items can be easily obtained by summing ``pages_sharing``,
    - ``pages_shared``, ``pages_unshared`` and ``pages_volatile``.
    + where ksm_saved_pages equals to the sum of ``pages_sharing`` +
    + ``ksm_zero_pages`` of the system, and all_rmap_items can be easily
    + obtained by summing ``pages_sharing``, ``pages_shared``, ``pages_unshared``
    + and ``pages_volatile``.

    2) The KSM profit inner a single process can be similarly obtained by the
    following approximate calculation::

    - process_profit =~ ksm_merging_pages * sizeof(page) -
    + process_profit =~ ksm_saved_pages * sizeof(page) -
    ksm_rmap_items * sizeof(rmap_item).

    - where ksm_merging_pages is shown under the directory ``/proc/<pid>/``,
    - and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``. The process profit
    - is also shown in ``/proc/<pid>/ksm_stat`` as ksm_process_profit.
    + where ksm_saved_pages equals to the sum of ``ksm_merging_pages`` and
    + ``ksm_zero_pages``, both of which are shown under the directory
    + ``/proc/<pid>/ksm_stat``, and ksm_rmap_items is alos shown in
    + ``/proc/<pid>/ksm_stat``. The process profit is also shown in
    + ``/proc/<pid>/ksm_stat`` as ksm_process_profit.

    From the perspective of application, a high ratio of ``ksm_rmap_items`` to
    ``ksm_merging_pages`` means a bad madvise-applied policy, so developers or
    diff --git a/mm/ksm.c b/mm/ksm.c
    index 4e510f5c5938..d23a240c2519 100644
    --- a/mm/ksm.c
    +++ b/mm/ksm.c
    @@ -3085,7 +3085,7 @@ static void wait_while_offlining(void)
    #ifdef CONFIG_PROC_FS
    long ksm_process_profit(struct mm_struct *mm)
    {
    - return mm->ksm_merging_pages * PAGE_SIZE -
    + return (long)(mm->ksm_merging_pages + mm->ksm_zero_pages) * PAGE_SIZE -
    mm->ksm_rmap_items * sizeof(struct ksm_rmap_item);
    }
    #endif /* CONFIG_PROC_FS */
    --
    2.15.2
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