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SubjectRe: [PATCH v4 00/10] sched/fair: rework the CFS load balance
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On 25/11/2019 12:48, Valentin Schneider wrote:
> I've been busy trying to get some perf numbers on arm64 server~ish systems,
> I finally managed to get some specjbb numbers on TX2 (the 2 nodes, 224
> CPUs version which I suspect is the same as you used in the above). I only
> have a limited number of iterations (5, although each runs for about 2h)
> because I wanted to get some (usable) results by today, I'll spin some more
> during the week.
>
>
> This is based on the "critical-jOPs" metric which AFAIU higher is better:
>
> Baseline, SMTOFF:
> mean 12156.400000
> std 660.640068
> min 11016.000000
> 25% 12158.000000
> 50% 12464.000000
> 75% 12521.000000
> max 12623.000000
>
> Patches (+ find_idlest_group() fixup), SMTOFF:
> mean 12487.250000
> std 184.404221
> min 12326.000000
> 25% 12349.250000
> 50% 12449.500000
> 75% 12587.500000
> max 12724.000000
>
>
> It looks slightly better overall (mean, stddev), but I'm annoyed by that
> low iteration count. I also had some issues with my SMTON run and I only
> got numbers for 2 iterations, so I'll respin that before complaining.
>
> FWIW the branch I've been using is:
>
> http://www.linux-arm.org/git?p=linux-vs.git;a=shortlog;h=refs/heads/mainline/load-balance/vincent_rework/tip
>

Forgot about that; I got some more results in the meantime, still specjbb
and still ThunderX2):

| kernel | count | mean | std | min | 50% | 75% | 99% | max |
|-----------------+-------+--------------+------------+---------+---------+----------+----------+---------|
| -REWORK SMT-ON | 15 | 19961.133333 | 613.406515 | 19058.0 | 20006.0 | 20427.50 | 20903.42 | 20924.0 |
| +REWORK SMT-ON | 12 | 19265.666667 | 563.959917 | 18380.0 | 19133.5 | 19699.25 | 20024.90 | 20026.0 |
| -REWORK SMT-OFF | 25 | 12397.000000 | 425.763628 | 11016.0 | 12377.0 | 12623.00 | 13137.20 | 13154.0 |
| +REWORK SMT-OFF | 20 | 12436.700000 | 414.130554 | 11313.0 | 12505.0 | 12687.00 | 12981.44 | 12986.0 |

SMT-ON delta: -3.48%
SMT-OFF delta: +0.32%


This is consistent with some earlier runs (where I had a few issues
getting enough iterations): SMT-OFF performs a tad better, and SMT-ON
performs slightly worse.

Looking at the 99th percentile, it seems we're a bit worse compared to
the previous best cases, but looking at the slightly reduced stddev it also
seems that we are somewhat more consistent.

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