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SubjectRe: [xfs] 610125ab1e: fsmark.app_overhead -71.2% improvement
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...

> 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...

Cheers,

Dave.
--
Dave Chinner
dchinner@redhat.com

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