https://bugzilla.kernel.org/show_bug.cgi?id=25252
--- Comment #11 from Ozlem Bilgir <ozlembil...@gmail.com> 2011-01-06 21:08:18
---
Hi Yakui,
Thanks for your response. I was experimenting on Xeon L5520. Now, I also
experiment on Westmere (X5650). Kernel version 2.6.37. I tried your patch on
both machines. I attached cpuinfo, powertop & turbostat outputs of the 2
machines with and without your patch for when all cores are online and when 1
core is offlined cases.
Here is the summary of what I observed;
1) Powertop vs turbostat: As you know, powertop reads time&usage of c-states
from the counters which kernel is collecting. Turbostat reads info from MSR.
Since turbostat is getting the info from hardware, I feel like it is more
realistic. (I'd appreciate if you comment on this).
2)About X5650
-Without the patch;
-Under very light load, when all cores are online, c6 usage of all cores
are almost 100% as can be seen from turbostat. Package c6 usage was around ~85%
for both packages. (You can see these from the turbostat_dump.xls attachment)
.Power consumption of the machine was ~55W. After core 23 is offlined, c6 usage
of sibling core (core 11 )decreased to 0% ( *5-10 min after* I disabled core
23). Package c6 usage is decreased to 0% for both packages. Power consumption
increased to ~70W. although powertop doesn't show decrease in c6 usage(c3 in
powertop notation), increase in power consumption tells the opposite. If both
core 23 & 11 were using c6 after core 23 is offlined as expected, I would
expect power consumption to be similar to having all cores online. This is
because
all cores were in deep sleep state most of the time and disabling one logical
core shouldn't have changed anything.
This also makes me believe turbostat output more than powertop.
-With the patch;
-similar results to without patch case.
3)About L5520,
-Without the patch;
-Similar to X5650. c6 usage of sibling core decreased to 0%, package c6
usage decreased to 0% after one core is offlined. Power consumption increased
from ~68W to ~79W.
-With patch;
-similar results to without patch case.
Ozlem
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