On 07/10/2012 05:58 PM, Yasuaki Ishimatsu wrote: > Hi Christoph, > > 2012/07/10 0:18, Christoph Lameter wrote: >> >> On Mon, 9 Jul 2012, Yasuaki Ishimatsu wrote: >> >>> Even if you apply these patches, you cannot remove the physical memory >>> completely since these patches are still under development. I want you to >>> cooperate to improve the physical memory hot-remove. So please review these >>> patches and give your comment/idea. >> >> Could you at least give a method on how you want to do physical memory >> removal? > > We plan to release a dynamic hardware partitionable system. It will be > able to hot remove/add a system board which included memory and cpu. > But as you know, Linux does not support memory hot-remove on x86 box. > So I try to develop it. > > Current plan to hot remove system board is to use container driver. > Thus I define the system board in ACPI DSDT table as a container device. > It have supported hot-add a container device. And if container device > has _EJ0 ACPI method, "eject" file to remove the container device is > prepared as follow: > > # ls -l /sys/bus/acpi/devices/ACPI0004\:01/eject > --w-------. 1 root root 4096 Jul 10 18:19 /sys/bus/acpi/devices/ACPI0004:01/eject > > When I hot-remove the container device, I echo 1 to the file as follow: > > #echo 1 > /sys/bus/acpi/devices/ACPI0004\:02/eject > > Then acpi_bus_trim() is called. And it calls acpi_memory_device_remove() > for removing memory device. But the code does not do nothing. > So I developed the continuation of the function. > >> You would have to remove all objects from the range you want to >> physically remove. That is only possible under special circumstances and >> with a limited set of objects. Even if you exclusively use ZONE_MOVEABLE >> you still may get cases where pages are pinned for a long time. > > I know it. So my memory hot-remove plan is as follows: > > 1. hot-added a system board > All memory which included the system board is offline. > > 2. online the memory as removable page > The function has not supported yet. It is being developed by Lai as follow: > http://lkml.indiana.edu/hypermail/linux/kernel/1207.0/01478.html > If it is supported, I will be able to create movable memory. > > 3. hot-remove the memory by container device's eject file We have implemented a prototype to do physical node (mem + CPU + IOH) hotplug for Itanium and is now porting it to x86. But with currently solution, memory hotplug functionality may cause 10-20% performance decrease because we concentrate all DMA/Normal memory to the first NUMA node, and all other NUMA nodes only hosts ZONE_MOVABLE. We are working on solution to minimize the performance drop now. > > Thanks, > Yasuaki Ishimatsu > >> >> I am not sure that these patches are useful unless we know where you are >> going with this. If we end up with a situation where we still cannot >> remove physical memory then this patchset is not helpful. > > > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
