On Sun, Jun 09, 2013 at 12:18:09AM +0200, Rafael J. Wysocki wrote:
> The average power drawn by the package is slightly higher with the
> patchset applied (27.66 W vs 27.25 W), but since the time needed to
> complete the workload with the patchset applied was shorter by about
> 2.3 sec, the total energy used was less in the latter case (by about
> 25.7 J if I'm not mistaken, or 1% relative). This means that in the
> absence of a power limit between 27.25 W and 27.66 W it's better to
> use the kernel with the patchset applied for that particular workload
> from the performance and energy usage perspective.
>
> Good, hopefully that's going to be confirmed on other systems and/or
> with other workloads. :-)
Yep, I see similar results on my AMD F15h.
So there's a register which tells you what the current energy
consumption in Watts is and support for it is integrated in lm_sensors.
I did one read per second, for the duration of the kernel build (10-r5 +
tip), with and without the patch, and averaged out the results:
without
=======
1. 158 samples, avg Watts: 116.915
2. 158 samples, avg Watts: 116.855
3. 158 samples, avg Watts: 116.737
4. 158 samples, avg Watts: 116.792
=> 116.82475 avg Watts.
with
====
1. 157 samples, avg Watts: 116.496
2. 156 samples, avg Watts: 117.535
3. 156 samples, avg Watts: 118.174
4. 157 samples, avg Watts: 117.95
=> 117.53875 avg Watts.
So there's a slight raise in the average power consumption but the
samples count drops by 1 or 2, which is consistent with the observed
kernel build speedup of 1 or 2 seconds.
perf doesn't show any significant difference with and without the patch
but those are single runs only.
without
=======
Performance counter stats for 'make -j9':
1167856.647713 task-clock # 7.272 CPUs utilized
1,071,177 context-switches # 0.917 K/sec
52,844 cpu-migrations # 0.045 K/sec
43,600,721 page-faults # 0.037 M/sec
4,712,068,048,465 cycles # 4.035 GHz
1,181,730,064,794 stalled-cycles-frontend # 25.08% frontend cycles idle
243,576,229,438 stalled-cycles-backend # 5.17% backend cycles idle
2,966,369,010,209 instructions # 0.63 insns per cycle
# 0.40 stalled cycles per insn
651,136,706,156 branches # 557.548 M/sec
34,582,447,788 branch-misses # 5.31% of all branches
160.599796045 seconds time elapsed
with
====
Performance counter stats for 'make -j9':
1169278.095561 task-clock # 7.271 CPUs utilized
1,076,528 context-switches # 0.921 K/sec
53,284 cpu-migrations # 0.046 K/sec
43,598,610 page-faults # 0.037 M/sec
4,721,747,687,668 cycles # 4.038 GHz
1,182,301,583,422 stalled-cycles-frontend # 25.04% frontend cycles idle
248,675,448,161 stalled-cycles-backend # 5.27% backend cycles idle
2,967,419,684,598 instructions # 0.63 insns per cycle
# 0.40 stalled cycles per insn
651,527,448,140 branches # 557.205 M/sec
34,560,656,638 branch-misses # 5.30% of all branches
160.811815170 seconds time elapsed
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
--
To unsubscribe from this list: send the line "unsubscribe cpufreq" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
