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

[Rong Chen]

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.

Best Regards,
Rong Chen