[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <20130530134718.GB32728@e103034-lin>
Date: Thu, 30 May 2013 14:47:18 +0100
From: Morten Rasmussen <morten.rasmussen@....com>
To: alex.shi@...el.com, peterz@...radead.org, mingo@...nel.org,
preeti@...ux.vnet.ibm.com, vincent.guittot@...aro.org,
efault@....de, pjt@...gle.com, linux-kernel@...r.kernel.org,
linaro-kernel@...ts.linaro.org
Cc: arjan@...ux.intel.com, len.brown@...el.com, corbet@....net,
tglx@...utronix.de
Subject: [RFC] Comparison of power-efficient scheduling patch sets
Hi,
A number of patch sets related to power-efficient scheduling have been
posted over the last couple of months. Most of them do not have much
data to back them up, so I decided to do some testing.
Common for all of the patch sets that I have tested, except one, is that
they attempt to pack tasks on as few cpus as possible to allow the
remaining cpus to enter deeper sleep states - a strategy that should
make sense on most platforms that support per-cpu power gating and
multi-socket machines.
Kernel: 3.9
Patch sets:
rlb-v4: sched: use runnable load based balance (Alex Shi)
<https://lkml.org/lkml/2013/4/27/13>
pas-v7: sched: power aware scheduling (Alex Shi)
<https://lkml.org/lkml/2013/4/3/732>
pst-v3: sched: packing small tasks (Vincent Guittot)
<https://lkml.org/lkml/2013/3/22/183>
pst-v4: sched: packing small tasks (Vincent Guittot)
<https://lkml.org/lkml/2013/4/25/396>
Configuration:
pas-v7: Set to "powersaving" mode.
pst-v4: Set to "Full" packing mode.
Platform:
ARM TC2 (test-chip), 2xCortex-A15 + 3xCortex-A7. Cortex-A15s disabled.
Measurement technique:
Time spent non-idle (not in idle state) for each cpu based on cpuidle
ftrace events. TC2 does not have per-core power-gating, so packing
inside the A7 cluster does not lead to any significant power savings.
Note that any product grade hardware (TC2 is a test-chip) will very
likely have per-core power-gating, so in those cases packing will have
an appreciable effect on power savings.
Measuring non-idle time rather than power should give a more clear idea
about the effect of the patch sets given that the idle back-end is
highly implementation specific.
Benchmarks:
audio playback (Android): 30s mp3 file playback on Android.
bbench+audio (Android): Web page rendering while doing mp3 playback.
andebench_native (Android): Android benchmark running in native mode.
cyclictest: Short periodic tasks.
Results:
Two runs for each patch set.
audio playback (Android) SMP
non-idle % cpu 0 cpu 1 cpu 2
3.9_1 11.96 2.86 2.48
3.9_2 12.64 2.81 1.88
rlb-v4_1 12.61 2.44 1.90
rlb-v4_2 12.45 2.44 1.90
pas-v7_1 16.17 0.03 0.24
pas-v7_2 16.08 0.28 0.07
pst-v3_1 15.18 2.76 1.70
pst-v3_2 15.13 0.80 0.38
pst-v4_1 16.14 0.05 0.00
pst-v4_2 16.34 0.06 0.00
bbench+audio (Android) SMP
non-idle % cpu 0 cpu 1 cpu 2 render time
3.9_1 25.00 20.73 21.22 812
3.9_2 24.29 19.78 22.34 795
rlb-v4_1 23.84 19.36 22.74 782
rlb-v4_2 24.07 19.36 22.74 797
pas-v7_1 28.29 17.86 16.01 869
pas-v7_2 28.62 18.54 15.05 908
pst-v3_1 29.14 20.59 21.72 830
pst-v3_2 27.69 18.81 20.06 830
pst-v4_1 42.20 13.63 2.29 880
pst-v4_2 41.56 14.40 2.17 935
andebench_native (8 threads) (Android) SMP
non-idle % cpu 0 cpu 1 cpu 2 Score
3.9_1 99.22 98.88 99.61 4139
3.9_2 99.56 99.31 99.46 4148
rlb-v4_1 99.49 99.61 99.53 4153
rlb-v4_2 99.56 99.61 99.53 4149
pas-v7_1 99.53 99.59 99.29 4149
pas-v7_2 99.42 99.63 99.48 4150
pst-v3_1 97.89 99.33 99.42 4097
pst-v3_2 99.16 99.62 99.42 4097
pst-v4_1 99.34 99.01 99.59 4146
pst-v4_2 99.49 99.52 99.20 4146
cyclictest SMP
non-idle % cpu 0 cpu 1 cpu 2
3.9_1 9.13 8.88 8.41
3.9_2 10.27 8.02 6.30
rlb-v4_1 8.88 8.09 8.11
rlb-v4_2 8.49 8.09 8.11
pas-v7_1 10.20 0.02 11.50
pas-v7_2 7.86 14.31 0.02
pst-v3_1 20.44 8.68 7.97
pst-v3_2 20.41 0.78 1.00
pst-v4_1 21.32 0.21 0.05
pst-v4_2 21.56 0.21 0.04
Overall, pas-v7 seems to do a fairly good job at packing. The idle time
distribution seems to be somewhere between pst-v3 and the more
aggressive pst-v4 for all the benchmarks. pst-v4 manages to keep two
cpus nearly idle (<0.25% non-idle) for both cyclictest and audio, which
is better than both pst-v3 and pas-v7. pas-v7 fails to pack cyclictest.
Packing does come at at cost which can be seen for bbench+audio, where
pst-v3 and rlb-v4 get better render times than pas-v7 and pst-v4 which
do more aggressive packing. rlb-v4 does not pack, it is only included
for reference.
>From a packing perspective pst-v4 seems to do the best job for the
workloads that I have tested on ARM TC2. The less aggressive packing in
pst-v3 may be a better choice for in terms of performance.
I'm well aware that these tests are heavily focused on mobile workloads.
I would therefore encourage people to share your test results for your
workloads on your platforms to complete the picture. Comments are also
welcome.
Thanks,
Morten
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists