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Re: [Xen-devel] [Xen-users] Xen 4.3.1 / Linux 3.12 panic

* Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> [2013-11-06 15:44:58 -0500]:

> Is there a particular reason you had tried 'cpufreq'? Sorry if that
> was answered earlier?

Ian suggested that the problem might be cpufreq related, (see
http://lists.xenproject.org/archives/html/xen-users/2013-11/msg00053.html )

> So the cpufreq=dom0 is kind of an nops as the Linux kernel will disable
> the native CPUfreq machinery. This is done b/c it does not make sense
> for Linux dom0 to control the CPU freq when it has no idea of the
> workloads (the hypervisor has it).

Aha. Not exactly what I understood from the xen documentation
(http://wiki.xen.org/wiki/Xen_power_management), but I was just testing it
to see if it would be stable.

> But with the 'cpufreq=dom0' you are getting faults.

With both cpufreq=dom0 and not specifying cpufreq at all, which defaults
to cpufreq=xen according to the docs the system will crash within the hour.
With cpufreq=none the system has now been stable for over a day without any
kernel warnings etc whatsoever (and I tried compiling a kernel for some load).

> So the other question is - does anything happen if you disable ACPI power
> states in the BIOS?

Let's try ;)
The BIOS has the following options that I consider relevant:
  Name         [Current] (Options)
- PowerNow     [Enabled]
- C State Mode [C6] (Disabled, C6)
- PowerCap     [P-state 0] (P-state 0 through 4)
- HPC Mode     [Enabled] (Disabled, Enabled)
- CPB Mode     [Auto] (Disabled, Auto)
- C1E Support  [Enabled] (Enabled, Disabled)

When I set PowerNow to disabled the C State Mode, PowerCap and HPC options also 
After booting with PowerNow disabled (without the cpufreq option) I tried a 
kernel compile
twice and some heavy I/O under which the system was stable.
So that seems to have the same effect as cpufreq=none.

- With PowerNow enabled (C State Mode and HPC / CPB Mode disabled ,no cpufreq 
the system also seems stable.
- C State Mode set to C6 (HPC/CPB disabled, no cpufreq cmdline), seems stable.
- HPC enabled, (CPB disabled, no cpufreq cmdline), crashed (serial console log 
as xen-crash-hpc-enabled).

These tests are inconclusive since I can't reliably trigger a panic, but it
usually happened within a few minutes when compiling a kernel or other load.
Even without load the system would crash mind you, just 'idling' it managed to 
as well but that often took longer.

Anyhow, please let me know if there's anything else I can test for you guys.
And thanks for the help :)



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