Hi Viresh,
On Fri, Jan 05, 2018 at 04:13:20PM +0530, Viresh Kumar wrote:
Hello,
I did some comparisons of Pelt and Walt and have some very interesting performance results that I wanted to share with all of you. I haven't got any power numbers as I don't have setup for that.
Key points:
All the tests were done on Hikey960, with a 5V Fan placed over the SoC to cool it down.
HDMI port was disconnected while running tests.
CONFIG_SCHED_TUNE was configured out to keep things simple.
Only the PCmark bench was tested, with help of workload automation.
Below number shows the average out of 3 runs, performed during a single kernel boot cycle.
Pelt 8/16/32 are the half-life periods.
While testing Pelt, CONFIG_WALT was disabled.
+------------------+----------+------------+------------+-----------+ | | | | | | | Test name | WALT | Pelt 8 ms | Pelt 16 ms | Pelt 32 ms| +------------------+----------+------------+------------+-----------+ | | | | | | | DataManipulation | 5341 | 5561 | 5453 | 5400 | | | | | | | | PhotoEditingV2 | 9015 | 8577 | 7911 | 6043 | | | | | | | | VideoEditing | 0 | 4291 | 3746 | 3755 | | | | | | | | WebV2 | 6202 | 6448 | 5465 | 4648 | | | | | | | | Workv2 | 0 | 5697 | 5069 | 4517 | | | | | | | | WritingV2 | 4302 | 4549 | 3811 | 3306 | +------------------+----------+------------+------------+-----------+
As you can see in the results Pelt 8 is very much comparable to the Walt results now. Hurray ? :)
A detailed report is present here with some more useful numbers:
How to replicate setup:
Android kernel tree: https://git.linaro.org/people/vireshk/mylinux.git android-4.9-hikey
This has several patches over latest 4.9-hikey aosp tree.
Some patches to reduce disturbances, which Vincent shared earlier with a document.
"thermal: Add debugfs support for cooling devices" and "cpufreq: stats: New sysfs attribute for clearing statistics" are used to read some more data from userspace after tests are done which can be used to build conclusions on working of pelt/walt and how they are behaving differently.
For example, we can know the amount of time we spent on individual cpu frequencies while the test was running. And also the time for which cpu-cooling and devfreq (ddr) has throttled some frequencies.
Pelt 16 and pelt 8 patches.
The below changes are required to capture the extra data that I have captured in my sheet above.
I have attached pelt_walt.sh script, which you need to push to /data:
$ adb push pelt_walt.sh /dataAnd I have updated the pcmark plugin file to run the script and collect data. That is attached as well.
Happy testing !!
I heard from Vincent earlier that ARM did similar testing earlier on but never found anything significant. Why ? I may have an answer to that, not sure though.
I may not be suitable person to answser this; just give some background info for this:
- I remembered Dietmar used Jankbench for comparing WALT and PELT, the scheduler signals have quite different effect on different testing case. Jankbench's tasks workload I think it's more related with responsiveness but from my understanding PCMark testing case is more related with sustainable workload?
Before I even observed the PELT signal (32ms period) might have better performance result than WALT for the sustainable workload, this is because the PELT signal has much longer decay time so it's more stable than WALT for some special case.
- I saw you have disabled SchedTune for testing, but SchedTune is quite fatal for Jankbench (Or Uibench) testing. The 'prefer_idle' and boost margin have quite important effect, even WALT signal also need heavily to rely on these knobs for Jankbench tunning. E.g 'prefer_idle' is fatal for reducing janks for UI cases.
Thanks, Leo Yan