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    Subject[PATCH 2/3] mm/util.c: make vm_memory_committed() more accurate
    Date
    percpu_counter_sum_positive() will provide more accurate info.

    Its time cost is about 800 nanoseconds on a 2C/4T platform and
    2~3 microseconds on a 2S/36C/72T server in normal case, and in
    worst case where vm_committed_as's spinlock is under severe
    contention, it costs 30~40 microseconds for the 2S/36C/72T sever,
    which should be fine for its two users: /proc/meminfo and HV ballon
    driver's status trace per second.

    Signed-off-by: Feng Tang <feng.tang@intel.com>
    ---
    mm/util.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/mm/util.c b/mm/util.c
    index 988d11e..3de78e9 100644
    --- a/mm/util.c
    +++ b/mm/util.c
    @@ -774,7 +774,7 @@ struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
    */
    unsigned long vm_memory_committed(void)
    {
    - return percpu_counter_read_positive(&vm_committed_as);
    + return percpu_counter_sum_positive(&vm_committed_as);
    }
    EXPORT_SYMBOL_GPL(vm_memory_committed);

    --
    2.7.4
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