On Wed, Sep 07, 2016 at 07:44:17AM -0400, Prarit Bhargava wrote: > The information in /sys/devices/system/cpu/cpuX/topology > directory is useful for userspace monitoring applications and in-tree > utilities like cpupower & turbostat. > > When down'ing a CPU the /sys/devices/system/cpu/cpuX/topology directory is > removed during the CPU_DEAD hotplug callback in the kernel. The problem > with this model is that the CPU has not been physically removed and the > data in the topology directory is still valid and the cpu's location is > now lost to userspace. > > This patch adds CONFIG_PERMANENT_CPU_TOPOLOGY, and is Y by default for > x86, an N for all other arches. When enabled the kernel is modified so > that the topology directory is added to the core cpu sysfs files so that > the topology directory exists while the CPU is physically present. When > disabled, the behavior of the current kernel is maintained (that is, the > topology directory is removed on a soft down and added on an soft up). > Adding CONFIG_PERMANENT_CPU_TOPOLOGY may require additional architecture > so that the cpumask data the CPU's topology is not cleared during a CPU > down.
So how do you physically remove things and how does the information then get removed? Also, why is that an x86 only feature?
