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    SubjectRe: [xfs] 610125ab1e: fsmark.app_overhead -71.2% improvement
    On Mon, Sep 09, 2019 at 02:06:54PM +0800, Rong Chen wrote:
    > Hi Dave,
    >
    > On 9/9/19 1:32 PM, Dave Chinner wrote:
    > > On Mon, Sep 09, 2019 at 09:58:49AM +0800, kernel test robot wrote:
    > > > Greeting,
    > > >
    > > > FYI, we noticed a -71.2% improvement of fsmark.app_overhead due to commit:
    > > A negative improvement? That's somewhat ambiguous...
    >
    > Sorry for causing the misunderstanding, it's a improvement not a regression.
    >
    >
    > >
    > > > 0e822255f95db400 610125ab1e4b1b48dcffe74d9d8
    > > > ---------------- ---------------------------
    > > > %stddev %change %stddev
    > > > \ | \
    > > > 1.095e+08 -71.2% 31557568 fsmark.app_overhead
    > > > 6157 +95.5% 12034 fsmark.files_per_sec
    > > So, the files/s rate doubled, and the amount of time spent in
    > > userspace by the fsmark app dropped by 70%.
    > >
    > > > 167.31 -47.3% 88.25 fsmark.time.elapsed_time
    > > > 167.31 -47.3% 88.25 fsmark.time.elapsed_time.max
    > > Wall time went down by 50%.
    > >
    > > > 91.00 -8.8% 83.00 fsmark.time.percent_of_cpu_this_job_got
    > > > 148.15 -53.2% 69.38 fsmark.time.system_time
    > > As did system CPU.
    > >
    > > IOWs, this change has changed create performance by a factor of 4 -
    > > the file create is 2x faster for half the CPU spent.
    > >
    > > I don't think this is a negative improvement - it's a large positive
    > > improvement. I suspect that you need to change the metric
    > > classifications for this workload...
    > To avoid misunderstanding, we'll use fsmark.files_per_sec instead of
    > fsmark.app_overhead in the subject.

    Well, the two are separate ways of measuring improvement. A change
    in one without a change in the other is just as significant as
    a change in both...

    Cheers,

    Dave.
    --
    Dave Chinner
    dchinner@redhat.com

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