Re: [RFC PATCH v4 1/2] sched/fair: Introduce short duration task check

[Dietmar Eggemann]

On 16/01/2023 10:33, Peter Zijlstra wrote:
> On Thu, Jan 05, 2023 at 12:33:16PM +0100, Dietmar Eggemann wrote:
>> On 16/12/2022 07:11, Chen Yu wrote:

[...]

> You were thinking of the dynamic PELT window size thread? (which is what
> I had to think of when I looked at this).

Yes, indeed.

> I think we can still do that with this prev_sum_exec_runtime_vol (can't
> say I love the name though). At any point (assuming we update
> sum_exec_runtime) sum_exec_runtime - prev_sum_exec_runtime_vol is the
> duration of the current activation.

I ran Jankbench with your UTIL_EST_FASTER patch and:

    runtime = curr->se.sum_exec_runtime -
              curr->se.prev_sum_exec_runtime_vol

plus:

    runtime >>= 10

before doing:

    util_est_fast = faster_est_approx(runtime * 2)
                                              ^^^ (boost)

on a Pixel6 and the results look promising:

Max frame duration (ms)

+-------------------+-----------+------------+
|      wa_path      | iteration |   value    |
+-------------------+-----------+------------+
|        base       |    10     | 147.571352 |
|    pelt-hl-m2     |    10     | 119.416351 |
|    pelt-hl-m4     |    10     | 96.473412  |
|  util_est_faster  |    10     | 84.834999  |
+-------------------+-----------+------------+

Mean frame duration (average case)

+---------------+-------------------+-------+-----------+
|   variable    |      kernel       | value | perc_diff |
+---------------+-------------------+-------+-----------+
| mean_duration |        base       | 14.7  |   0.0%    |
| mean_duration |    pelt-hl-m2     | 13.6  |   -7.5%   |
| mean_duration |    pelt-hl-m4     | 13.0  |  -11.68%  |
| mean_duration |  util_est_faster  | 12.6  |  -14.01%  |
+---------------+-------------------+-------+-----------+

Jank percentage

+-----------+-------------------+-------+-----------+
| variable  |      kernel       | value | perc_diff |
+-----------+-------------------+-------+-----------+
| jank_perc |        base       |  1.8  |   0.0%    |
| jank_perc |    pelt-hl-m2     |  1.8  |  -4.91%   |
| jank_perc |    pelt-hl-m4     |  1.2  |  -36.61%  |
| jank_perc |  util_est_faster  |  0.8  |  -57.8%   |
+-----------+-------------------+-------+-----------+

Power usage [mW]

+--------------+-------------------+-------+-----------+
|  chan_name   |      kernel       | value | perc_diff |
+--------------+-------------------+-------+-----------+
| total_power  |        base       | 144.4 |   0.0%    |
| total_power  |    pelt-hl-m2     | 141.6 |  -1.97%   |
| total_power  |    pelt-hl-m4     | 163.2 |  12.99%   |
| total_power  |  util_est_faster  | 150.9 |   4.45%   |
+--------------+-------------------+-------+-----------+

At first glance it looks promising! Have to do more testing to
understand the behaviour fully.