" " " >From Intel Manual: No additional power reduction actions are taken in the package C1 state. However, if the C1E substate is enabled, the processor automatically transitions to the lowest supported core clock frequency, followed by a reduction in voltage. Autonomous power reduction actions which are based on idle timers, can trigger depending on the activity in the system. The package enters the C1 low power state when: • At least one core is in the C1 state. • The other cores are in a C1 or lower power state. The package enters the C1E state when: • All cores have directly requested C1E via MWAIT(C1) with a C1E sub-state hint. • All cores are in a power state lower that C1/C1E but the package low power state is limited to C1/C1E via the PMG_CST_CONFIG_CONTROL MSR. • All cores have requested C1 using HLT or MWAIT(C1) and C1E auto-promotion is enabled in POWER_CTL. No notification to the system occurs upon entry to C1/C1E. " " "
Whenever Linux request a MWAIT instruction the cores will be put into C1E state (as you can see on the second powertop screenshot). I recommend anyone to apply this workaround slowly in a big number of nodes environment (if a reboot can't be made). This will allow you to follow power consumption and heat generated by this change. >From the suggested KERNEL CMDLINE (GRUB): "intel_idle.max_cstate=0 nox2apic intremap=off" intel_idle.max_cstates=0 will disable intel_idle module and enable acpi_idle module respecting proper BIOS ACPI tables. Next: To understand what is causing this behavior from intel_idle code (not respecting ACPI tables and maybe causing NMIs trying to manage C-states not compatible with processor type). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1318551 Title: Kernel Panic - not syncing: An NMI occurred, please see the Integrated Management Log for details. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1318551/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
