On Mon, 10 Sep 2018 15:26:55 +0000 Pasha Tatashin <[email protected]> wrote:
> > I agree memoryblock is a hack, it fails to do both things it was > designed to do: > > 1. On bare metal you cannot free a physical dimm of memory using > memoryblock granularity because memory devices do not equal to physical > dimms. Thus, if for some reason a particular dimm must be > remove/replaced, memoryblock does not help us. > > 2. On machines with hypervisors it fails to provide an adequate > granularity to add/remove memory. > > We should define a new user interface where memory can be added/removed > at a finer granularity: sparse section size, but without a memory > devices for each section. We should also provide an optional access to > legacy interface where memory devices are exported but each is of > section size. > > So, when legacy interface is enabled, current way would work: > > echo offline > /sys/devices/system/memory/memoryXXX/state > > And new interface would allow us to do something like this: > > echo offline 256M > /sys/devices/system/node/nodeXXX/memory > > With optional start address for offline memory. > echo offline [start_pa] size > /sys/devices/system/node/nodeXXX/memory > start_pa and size must be section size aligned (128M). > > It would probably be a good discussion for the next MM Summit how to > solve the current memory hotplug interface limitations. Please keep lsmem/chmem from util-linux in mind, when changing the memory hotplug user interface.
