Re: [8/8,v3] NUMA Hotplug Emulator: documentation

Américo Wang
2010-11-21T15:00:44Z

On Wed, Nov 17, 2010 at 10:08:07AM +0800, shaohui.zheng@intel.com wrote:
>+2) CPU hotplug emulation:
>+
>+The emulator reserve CPUs throu grub parameter, the reserved CPUs can be
>+hot-add/hot-remove in software method, it emulates the process of physical
>+cpu hotplug.
>+
>+When hotplug a CPU with emulator, we are using a logical CPU to emulate the CPU
>+socket hotplug process. For the CPU supported SMT, some logical CPUs are in the
>+same socket, but it may located in different NUMA node after we have emulator.
>+We put the logical CPU into a fake CPU socket, and assign it an unique
>+phys_proc_id. For the fake socket, we put one logical CPU in only.
>+
>+ - to hide CPUs
>+ - Using boot option "maxcpus=N" hide CPUs
>+ N is the number of initialize CPUs
>+ - Using boot option "cpu_hpe=on" to enable cpu hotplug emulation
>+ when cpu_hpe is enabled, the rest CPUs will not be initialized
>+
>+ - to hot-add CPU to node
>+ $ echo nid > cpu/probe
>+
>+ - to hot-remove CPU
>+ $ echo nid > cpu/release
>+

Again, we already have software CPU hotplug,
i.e. /sys/devices/system/cpu/cpuX/online.

You need to pick up another name for this.

>From your documentation above, it looks like you are trying
to move one CPU between nodes?

>+ cpu_hpe=on/off
>+ Enable/disable cpu hotplug emulation with software method. when cpu_hpe=on,
>+ sysfs provides probe/release interface to hot add/remove cpu dynamically.
>+ this option is disabled in default.
>+

Why not just a CONFIG? IOW, why do we need to make another boot
parameter for this?