Red Hat Bugzilla – Bug 448151
Throttling seems weird, doesn't appear to enter C-states, runs hot
Last modified: 2008-11-12 03:56:52 EST
Description of problem:
The information under /proc/acpi/processor/CPU?/throttling seems odd. First, the
CPU never seemed to enter even C1. [Normally, I'd expect to see it in C1 some of
the time, I have to boot nohz=off because of another bug: see Bug 443155] This
is probably why the system is idling a good few degrees higher under this kernel.
Throttling seems different as well. Under kernel-22.214.171.124-92.fc8,
CPU0/throttling would be:
Could not determine current throttling state.
but CPU1/throttling had:
state count: 8
active state: T0
state available: T0 to T7
Under 126.96.36.199-10.fc8, CPU0/throttling is now like CPU1 EXCEPT the asterisk is
stuck on the T3 state.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
For acpidump, see bug 448150.
Same with kernel-188.8.131.52-14.fc8, eats battery.
Enters C-states when I remove "nohz=off" with kernel-184.108.40.206-24.fc8, but
throttling oddness remains and still seems to run hotter than
Things still seem odd with kernel-220.127.116.11-27.fc8. powertop reports a few
hundred wakeups per second here and the processor spending a good amount of time
in C3 (but perhaps this is not what the hardware is *actually* doing), so
nothing unusual there... but sometimes powertop reports garbage (e.g., tens of
thousands --- or even a negative number --- of wups) and the sysfs counts for
C-state usage seem to reset every so often.
Even odder in kernel-18.104.22.168-37.fc8, throttling for both cores seems suck in T8.
Back to same throttling strangeness as 22.214.171.124-10.fc8 with
kernel-126.96.36.199-62.fc8 (see opening comment). kernel-188.8.131.52-92.fc8 runs
cooler on this machine with "nohz=off" than 184.108.40.206-10.fc8 in tickless mode.
Still present in kernel-220.127.116.11-14.fc8.
Appears to be fixed in kernel-18.104.22.168-32.fc9.x86_64, until a suspend/resume cycle. Will report a new bug.