Tickless kernel and C-states on Turion 64

[Johan Brannlund]

Hi. I just tried powertop and noticed a few issues when running it on my single-core Turion 64 laptop (ATI IXP chipset) with a 64-bit 2.6.23-hrt1 kernel (2.6.23 with patchset from http://www.kernel.org/pub/linux/kernel/people/tglx/hrtimers/2.6.23/)

1. The processor never enters any C-states apart from C0, not even if I run in console mode with all non-essential kernel modules and programs stopped. Booting with various combinations of "noapic nolapic nolapic_timer" doesn't help either. Why is this? It seems like my processor should support C-states:

# cat /proc/acpi/processor/C000/power 
active state:            C0
max_cstate:              C8
bus master activity:     00000000
maximum allowed latency: 8000 usec
states:
    C1:                  type[C1] promotion[--] demotion[--] latency[000] usage[00000000] duration[00000000000000000000]
    C2:                  <not supported>
    C3:                  type[C3] promotion[--] demotion[--] latency[010] usage[00000000] duration[00000000000000000000]

# cat /proc/acpi/processor/C000/info 
processor id:            0
acpi id:                 1
bus mastering control:   yes
power management:        yes
throttling control:      yes
limit interface:         yes


2. I'm not sure that HPET is actually enabled. I did select it in the kernel config, but there's nothing about HPET in the logs. How can I tell for sure? Kernel config:

# grep HZ /boot/config-2.6.23-hrt1 
CONFIG_NO_HZ=y
# CONFIG_HZ_100 is not set
CONFIG_HZ_250=y
# CONFIG_HZ_300 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=250

# grep HPET /boot/config-2.6.23-hrt1 
CONFIG_HPET_TIMER=y
CONFIG_HPET_EMULATE_RTC=y
CONFIG_HPET=y
# CONFIG_HPET_RTC_IRQ is not set
CONFIG_HPET_MMAP=y


Thanks in advance,

Johan





       
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