Re: [RESEND PATCH v2 0/2] Enable Odroid-XU3/4 to use Energy Model and Energy Aware Scheduler
From: Lukasz Luba
Date: Fri Feb 28 2020 - 07:00:18 EST
Hi Marek,
On 2/28/20 10:59 AM, Marek Szyprowski wrote:
Hi Lukasz
On 21.02.2020 11:32, Lukasz Luba wrote:
On 2/20/20 6:00 PM, Krzysztof Kozlowski wrote:
On Thu, Feb 20, 2020 at 09:56:34AM +0000, Lukasz Luba wrote:
This is just a resend, now with proper v2 in the patches subject.
The Odroid-XU4/3 is a decent and easy accessible ARM big.LITTLE
platform,
which might be used for research and development.
This small patch set provides possibility to run Energy Aware
Scheduler (EAS)
on Odroid-XU4/3 and experiment with it.
The patch 1/2 provides 'dynamic-power-coefficient' in CPU DT nodes,
which is
then used by the Energy Model (EM).
The patch 2/2 enables SCHED_MC (which adds another level in
scheduling domains)
and enables EM making EAS possible to run (when schedutil is set as
a CPUFreq
governor).
1. Test results
Two types of different tests have been executed. The first is energy
test
case showing impact on energy consumption of this patch set. It is
using a
synthetic set of tasks (rt-app based). The second is the performance
test
case which is using hackbench (less time to complete is better).
In both tests schedutil has been used as cpufreq governor. In all tests
PROVE_LOCKING has not been compiled into the kernels.
1.1 Energy test case
10 iterations of 24 periodic rt-app tasks (16ms period, 10% duty-cycle)
with energy measurement. The cpufreq governor - schedutil. Unit is
Joules.
The energy is calculated based on hwmon0 and hwmon3 power1_input.
The goal is to save energy, lower is better.
+-----------+-----------------+------------------------+
|ÂÂÂÂÂÂÂÂÂÂ | Without patches | With patchesÂÂÂÂÂÂÂÂÂÂ |
+-----------+--------+--------+----------------+-------+
| benchmark | Mean | RSD* | Mean | RSD* |
+-----------+--------+--------+----------------+-------+
| 24 rt-app |Â 21.56 |Â 1.37% |Â 19.85 (-9.2%) | 0.92% |
| tasks | | | | |
+-----------+--------+--------+----------------+-------+
1.2 Performance test case
10 consecutive iterations of hackbench (hackbench -l 500 -s 4096),
no delay between two successive executions.
The cpufreq governor - schedutil. Units in seconds.
The goal is to see not regression, lower completion time is better.
+-----------+-----------------+------------------------+
|ÂÂÂÂÂÂÂÂÂÂ | Without patches | With patchesÂÂÂÂÂÂÂÂÂÂ |
+-----------+--------+--------+----------------+-------+
| benchmark | MeanÂÂ | RSD*ÂÂ | MeanÂÂÂÂÂÂÂÂÂÂ | RSD*Â |
+-----------+--------+--------+----------------+-------+
| hackbench |Â 8.15Â | 2.86%Â |Â 7.95 (-2.5%)Â | 0.60% |
+-----------+--------+--------+----------------+-------+
*RSD: Relative Standard Deviation (std dev / mean)
Nice measurements!
Glad to hear that.
Applied both, thank you.
Thank you for applying this.
After applying the patches I see the following warnings during boot (XU4):
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 1 >= em_cap_state0
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 3 >= em_cap_state2
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 4 >= em_cap_state3
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 5 >= em_cap_state4
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 8 >= em_cap_state7
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 10 >= em_cap_state9
energy_model: pd0: hertz/watts ratio non-monotonically decreasing:
em_cap_state 11 >= em_cap_state10
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 1 >= em_cap_state0
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 2 >= em_cap_state1
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 3 >= em_cap_state2
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 4 >= em_cap_state3
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 5 >= em_cap_state4
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 6 >= em_cap_state5
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 8 >= em_cap_state7
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 9 >= em_cap_state8
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 10 >= em_cap_state9
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 13 >= em_cap_state12
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 15 >= em_cap_state14
energy_model: pd4: hertz/watts ratio non-monotonically decreasing:
em_cap_state 16 >= em_cap_state15
Is it okay?
It shouldn't harm the EAS but it might be used by thermal, especially
those OPPs from the top. Like in your case in step_wise (IIRC the DT
settings).
But removing some of these from the bottom, would be good.
It would lower the Energy Model complexity, which is:
nr_perf_domain * (nr_cpus + nr_OPPs) [1] (in Odroid XU4 is ~80 IIRC)
smaller OPP number is better.
Douglas is working on a patch set which could skip non-efficient OPPs
(the OPPs which have the same voltage but different frequency).
Although, we don't know the numbers how much it could save energy - when
we use the fastest frequency for the set of OPPs with the same voltage,
comparing to the slowest (theoretically entering idle earlier) .
The discussion is ongoing here [2].
Regarding the print message. It's not a bug in the platform so in
my opinion we shouldn't use 'pr_warn' in this case.
It's going to be changed to just debug level print. I have this
change in the new Energy Model. It is in last point in changelog v3 [3]
and the change which does this is in patch 1/4:
--------------------------------------------->8------------------
- pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing:
em_cap_state %d >= em_cap_state%d\n",
- cpu, i, i - 1);
+ dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing:
em_perf_state %d >= em_perf_state%d\n",
+ i, i - 1);
--------------------------------------8<------------------------
Regards,
Lukasz
[1]
https://elixir.bootlin.com/linux/latest/source/kernel/sched/topology.c#L397
[2] https://lkml.org/lkml/2020/1/22/1169
[3] https://lkml.org/lkml/2020/2/21/1910