Kernel configuration

This article summarises various kernel configuration issues.

ACPI sleep

It is a bit tricky to make ACPI sleep and OpenVZ work together.

ACPI sleep is enabled by ACPI_SLEEP kernel option. The following dependencies are declared in kernel configs:

ACPI_SLEEP depends on X86 && (!SMP || SUSPEND_SMP)
SUSPEND_SMP depends on HOTPLUG_CPU && X86 && PM
FAIRSCHED depends on SCHED_VCPU

And SCHED_VCPU is incompatible with HOTPLUG_CPU:

./kernel/cpu.c:#error "CONFIG_HOTPLUG_CPU isn't supported with CONFIG_SCHED_VCPU"

On non-SMP machine, you may disable SMP, this will resolve the conflict.

If you have SMP machine, you can only disable FAIRSCHED and SCHED_VCPU. This will loose some isolation between VEs (CPU scheduling will be performed per-task, not per-VE, and cpuunits and cpulimit settings will not take effect), but it is acceptable solution if your VEs are trusted (and it's hard to imagine untrusted VEs on a notebook ;)