http://bugzilla.kernel.org/show_bug.cgi?id=15157
Len Brown <l...@kernel.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |acpi-bugzi...@lists.sourcef
| |orge.net
Component|Power-Processor |BIOS
Resolution| |DOCUMENTED
AssignedTo|l...@kernel.org |acpi_b...@kernel-bugs.osdl.
| |org
--- Comment #1 from Len Brown <l...@kernel.org> 2010-01-28 05:56:51 ---
booting without maxcpus=1, this problem goes away.
All the cores are able to enter c6 and get their frequency down to 1.6GHz
for the short time they are in c0:
CPU GHz TSC %c0 %c1 %c3 %c6 %pc3 %pc6 %pc7
0 1.60 2.80 0.16 0.23 0.00 99.61 0.00 98.95 0.00
1 1.60 2.80 0.08 0.09 0.00 99.83 0.00 98.95 0.00
2 1.60 2.80 0.01 0.02 0.00 99.96 0.00 98.95 0.00
3 1.63 2.80 0.01 0.03 0.00 99.96 0.00 98.95 0.00
4 1.60 2.80 0.01 0.02 0.00 99.98 0.00 98.96 0.00
5 1.60 2.80 0.06 0.13 0.00 99.81 0.00 98.96 0.00
6 1.58 2.80 0.01 0.02 0.00 99.97 0.00 98.96 0.00
7 1.60 2.80 0.01 0.02 0.00 99.98 0.00 98.96 0.00
8 1.60 2.80 0.04 0.35 0.00 99.61 0.00 98.95 0.00
9 1.60 2.80 0.02 0.15 0.00 99.83 0.00 98.95 0.00
10 1.60 2.80 0.01 0.03 0.00 99.96 0.00 98.95 0.00
11 1.59 2.80 0.01 0.03 0.00 99.96 0.00 98.95 0.00
12 1.57 2.80 0.01 0.02 0.00 99.98 0.00 98.96 0.00
13 1.60 2.80 0.04 0.15 0.00 99.81 0.00 98.96 0.00
14 1.63 2.80 0.01 0.02 0.00 99.97 0.00 98.96 0.00
15 1.60 2.80 0.01 0.01 0.00 99.98 0.00 98.96 0.00
When a cycle soaker is run, it is able to turbo-up to 3.2GHz as expected:
CPU GHz TSC %c0 %c1 %c3 %c6 %pc3 %pc6 %pc7
0 3.20 2.80 1.91 6.24 3.63 88.22 0.00 0.00 0.00
1 3.19 2.80 0.05 99.95 0.00 0.00 0.00 0.00 0.00
2 2.90 2.80 0.02 0.09 84.97 14.92 0.00 0.00 0.00
3 2.49 2.80 0.01 0.09 84.98 14.92 0.00 0.00 0.00
4 1.60 2.80 0.14 0.21 0.00 99.65 0.00 0.00 0.00
5 1.60 2.80 0.05 0.10 0.00 99.85 0.00 0.00 0.00
6 1.63 2.80 0.01 0.02 0.00 99.98 0.00 0.00 0.00
7 1.60 2.80 0.01 0.02 0.00 99.98 0.00 0.00 0.00
8 3.20 2.80 2.24 5.91 3.63 88.22 0.00 0.00 0.00
9 3.20 2.80 99.99 0.01 0.00 0.00 0.00 0.00 0.00
10 2.53 2.80 0.01 0.10 84.98 14.91 0.00 0.00 0.00
11 2.51 2.80 0.01 0.09 84.98 14.92 0.00 0.00 0.00
12 1.60 2.80 0.07 0.29 0.00 99.65 0.00 0.00 0.00
13 1.60 2.80 0.04 0.10 0.00 99.85 0.00 0.00 0.00
14 1.60 2.80 0.01 0.02 0.00 99.98 0.00 0.00 0.00
15 1.60 2.80 0.01 0.01 0.00 99.98 0.00 0.00 0.00
The "maxcpus=1" power-management failure is due to a BIOS bug.
The BIOS is supposed to put non-boot CPUSs into c6
so that if the OS does not start them, they will not interfere with
power management. However, this BIOS is clearly leaving the non-boot
CPUs in c1, which interferes with the power-management of the online cpus.
This same symptom is seen when a kernel built for MAX_CPUS=8
is run on a 16-thread system (which is how I first noticed this problem).
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