Hi Morten,
On Thu, Oct 27, 2016 at 02:38:12PM +0100, Morten Rasmussen wrote:
[...]
o Testing result:
Tested hackbench on Hikey with CA53x8 CPUs with SMP load balance:
time sh -c 'for i in `seq 100`; do /data/hackbench -p -P > /dev/null; done' real user system baseline 6m00.57s 1m41.72s 34m38.18s rb tree 5m55.79s 1m33.68s 34m08.38s
For hackbench test case we can see with rb tree it even has better result than baseline kernel.
It is around 1% difference, so pretty much in the noise? Have tried longer runs of hackbench? For the capacity awareness postings I'm using:
Sorry in my previous testing I wrongly used WALT signals, so please ignore it.
I did more testing on it for PELT signals, below are testing result:
baseline: 5m57.86s real 1m42.36s user 34m23.30s system (PELT) 5m56.60s real 1m41.45s user 34m16.23s system (PELT)
with rb-tree patches: 5m43.84s real 1m35.82s user 32m56.43s system (PELT) 5m46.67s real 1m35.39s user 33m18.07s system (PELT)
The real run time is not decreased too much (10s ~ 14s), but we can see the system time can decrease obviously (58.16s ~ 86.97s) for multi-core's processing.
perf stat --null --repeat 10 -- \ perf bench sched messaging -g 50 -l 1000I'm still curious how many tasks that are actually on the rq for hackbench, but it seems that overhead isn't a major issue.
From the code, at the same time hackbench launches 40 processes (20
processes for messager's senders and 20 for receivers).
Do you think this is similiar testing with perf you meantioned?
Tested video playback on Juno for LB_MIN vs rb tree:
LB_MIN Nrg:LITTLE Nrg:Big Nrg:Sum
11.3122 8.983429 20.295629 11.337446 8.174061 19.511507 11.256941 8.547895 19.804836 10.994329 9.633028 20.627357 11.483148 8.522364 20.005512 avg. 11.2768128 8.7721554 20.0489682stdev 0.431777914rb tree Nrg:LITTLE Nrg:Big Nrg:Sum
11.384301 8.412714 19.797015 11.673992 8.455219 20.129211 11.586081 8.414606 20.000687 11.423509 8.64781 20.071319 11.43709 8.595252 20.032342 avg. 11.5009946 8.5051202 20.0061148stdev 0.1263371635vs LB_MIN +1.99% -3.04% -0.21%Should I read this as the energy benefits of the rb-tree solution is the negligible? It seems to be much smaller than the error margins.
From the power data on Juno, the final difference is quite small. But
if we review the energy for big cluster and little cluster, we can see the benefit by reducing big core's energy and uses more LITTLE core for tasks.
From my previous experience, the power optimization patches can save
power 10% on another b.L system for camera case, but it only can save CPU power 2.97% for video playback on Juno. This is caused by video playback still have no enough small tasks, for the case with many small tasks we can see more benefit.
Do you have suggestion for power testing case on Juno?
Does we have evidence that the util-rb-tree solution is any better than using LB_MIN?
I think the evidence is big core saving 3.04% energy than LB_MIN, this is not big difference on Juno. The difference is possible to enlarged for the scenario with many tasks (like camera case).
But yes, this should be verified on other SoCs for more confidence.
Thanks, Leo Yan