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SubjectRe: [RFC PATCH 0/3] sched: Introduce Window Assisted Load Tracking
On 2016-10-28 01:49, Peter Zijlstra wrote:
> On Fri, Oct 28, 2016 at 12:57:05AM -0700, Vikram Mulukutla wrote:
>> On 2016-10-28 00:49, Peter Zijlstra wrote:
>> >On Fri, Oct 28, 2016 at 12:10:39AM -0700, Vikram Mulukutla wrote:
>> >>This RFC patch has been tested on live X86 machines with the following
>> >>sanity
>> >>and benchmark results (thanks to Juri Lelli, Dietmar Eggeman, Patrick
>> >>Bellasi
>> >>for initial code reviews):
>> >>
>> >>(Tested on an Intel i7 2nd generation CPU, 8GB RAM, Nvidia GTX950Ti
>> >>graphics,
>> >>with the same frequency list as above. Running Ubuntu 16.04 on a v4.8.2
>> >>baseline. WALT window size was 10ms. Only deltas above 3% are considered
>> >>non-noise.Power measured with Intel RAPL counters)
>> >
>> >Was this comparison done using the use_walt_metric sysctl knob?
>>
>> Yes, it was. You will want to see numbers against a pure 4.8.2 without
>> any
>> of the WALT code, correct?
>
> Yep, because with the sysctl we still run all the accounting code. So
> esp things like the hackbench run are meaningless (note that even the
> CONFIG thing doesn't take out everything).
>
> Also, I think it makes sense to always (also) compare against the
> "performance" governor. That way you can see the drop in absolute
> performance etc..

Ok, here are some numbers. I should be able to get the rest during the
week.
The averages are pretty close, so I figured I would include some
percentile
numbers. PELT and WALT numbers are with schedutil. On average it seems
we're
introducing about 0.5% overhead with the current additional accounting.

Test: perf bench sched messaging -g 50 -l 5000
+-------------+-------------+----------+----------+-----------+
| 4.8.2-walt | Performance | Ondemand | PELT | WALT(10ms)|
+-------------+-------------+----------+----------+---------- +
| | | | | |
| 90th | 17.077 | 17.088 | 17.088 | 17.159 |
| | | | | |
| 96th | 17.117 | 17.421 | 17.198 | 17.343 |
| | | | | |
| Average | 16.910 | 16.916 | 16.937 | 16.962 |
| | | | | |
+-------------+-------------+----------+----------+-----------+
| 4.8.2-raw | Performance | Ondemand | PELT | WALT(10ms)|
+-------------+-------------+----------+----------+-----------+
| | | | | |
| 90th | 16.919 | 17.1694 | 16.986 | 0 |
| | | | | |
| 96th | 16.980 | 17.364 | 17.052 | 0 |
| | | | | |
| Average | 16.841 | 16.902 | 16.860 | 0 |
+-------------+-------------+----------+----------+-----------+

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