I've been looking at Xen (3.4.2) power management, and have been trying
out different settings. One machine I tried was a Toshiba M30 laptop,
which has an Intel Core 2 Duo CPU:
CPU0: Intel(R) Core(TM)2 Duo CPU P8400 @ 2.26GHz stepping 06
CPU1: Intel(R) Core(TM)2 Duo CPU P8400 @ 2.26GHz stepping 06
When dom0 initialized power management, the messages printed are as follows:
Set CPU acpi_id(0) cpuid(0) Px State info:
_PCT: descriptor=0, length=0, space_id=127, bit_width=0, bit_offset=0,
reserved=0, address=0
_PCT: descriptor=0, length=0, space_id=127, bit_width=0, bit_offset=0,
reserved=0, address=0
_PSS: state_count=4
State0: 2261MHz 35000mW 10us 10us 0x927 0x927
State1: 2260MHz 35000mW 10us 10us 0x4822 0x4822
State2: 1600MHz 16000mW 10us 10us 0x617 0x617
State3: 800MHz 14300mW 10us 10us 0x8611 0x8611
_PSD: num_entries=5 rev=0 domain=0 coord_type=252 num_processors=1
_PPC: 0
xen_pminfo: @acpi_cpufreq_cpu_init,HARDWARE addr space
CPU 0 initialization completed
Set CPU acpi_id(1) cpuid(1) Px State info:
_PCT: descriptor=0, length=0, space_id=127, bit_width=0, bit_offset=0,
reserved=0, address=0
_PCT: descriptor=0, length=0, space_id=127, bit_width=0, bit_offset=0,
reserved=0, address=0
_PSS: state_count=4
State0: 2261MHz 35000mW 10us 10us 0x927 0x927
State1: 2260MHz 35000mW 10us 10us 0x4822 0x4822
State2: 1600MHz 16000mW 10us 10us 0x617 0x617
State3: 800MHz 14300mW 10us 10us 0x8611 0x8611
_PSD: num_entries=5 rev=0 domain=1 coord_type=252 num_processors=1
_PPC: 0
xen_pminfo: @acpi_cpufreq_cpu_init,HARDWARE addr space
CPU 1 initialization completed
cpuid.MWAIT[.eax=40, .ebx=40, .ecx=3, .edx=3122220]
Monitor-Mwait will be used to enter C-1 state
cpuid.MWAIT[.eax=40, .ebx=40, .ecx=3, .edx=3122220]
Monitor-Mwait will be used to enter C-1 state
It seems to mostly work ok, except that an OpenSolaris HVM domU slows
down to a crawl. When I examined it, I noticed that it wasn't getting
any timer interrupts. Or, almost none; occasionally the interrupt count
for the timer jumps, but mostly it stays frozen.
If I limit the maximum C state to C2, things seem ok, but when C3 is
used, the problems pops up pretty quickly, though not immediately: if I
initialize the maximum C state to 1, but then change it to C3 when the
domU is already running, it won't immediately slow down, it might take
about a minute, during which time the xenpm utility already is showing
that C3 is being used. So a switch to C3 isn't guaranteed to cause the
problem, but it eventually will.
I tried other HVM domains, such as Windows, and they don't seem to have
the problem. But, they might be more "tickless" than OpenSolaris is.
I haven't looked at the PM code much yet, and I haven't tried -unstable,
but there don't seem to be any changes in -unstable that would fix this.
Is this a known problem? Any hints for diagnosing the problem?
- Frank
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