linux-kernel - Re: [PATCH 0/4 v4] sched/rt: track rt rq utilization

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Date:   Sun, 15 Apr 2018 13:56:53 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>, peterz@...radead.org,
        mingo@...nel.org, linux-kernel@...r.kernel.org, rjw@...ysocki.net
Cc:     juri.lelli@...hat.com, Morten.Rasmussen@....com,
        viresh.kumar@...aro.org, valentin.schneider@....com
Subject: Re: [PATCH 0/4 v4] sched/rt: track rt rq utilization

On 03/16/2018 12:25 PM, Vincent Guittot wrote:

[...]

> For a 15 seconds long test on a hikey 6220 (octo core cortex A53 platfrom),
> the cpufreq statistics outputs (stats are reset just before the test) :
> $ cat /sys/devices/system/cpu/cpufreq/policy0/stats/total_trans
> without patchset : 1230
> with patchset : 14
> 
> If we replace the cfs thread of rt-app by a sysbench cpu test, we can see
> performance improvements:
> 
> - Without patchset :
> Test execution summary:
>      total time:                          15.0009s
>      total number of events:              4903
>      total time taken by event execution: 14.9972
>      per-request statistics:
>           min:                                  1.23ms
>           avg:                                  3.06ms
>           max:                                 13.16ms
>           approx.  95 percentile:              12.73ms
> 
> Threads fairness:
>      events (avg/stddev):           4903.0000/0.00
>      execution time (avg/stddev):   14.9972/0.00
> 
> - With patchset:
> Test execution summary:
>      total time:                          15.0014s
>      total number of events:              7694
>      total time taken by event execution: 14.9979
>      per-request statistics:
>           min:                                  1.23ms
>           avg:                                  1.95ms
>           max:                                 10.49ms
>           approx.  95 percentile:              10.39ms
> 
> Threads fairness:
>      events (avg/stddev):           7694.0000/0.00
>      execution time (avg/stddev):   14.9979/0.00
> 
> The performance improvement is 56% for this use case.

How do you get this number? Normally we use the 'total time' value.

[...]