On Wed, 16 Mar 2016 10:11:54 +0530 Bharata B Rao <[email protected]> wrote:
> On Wed, Mar 16, 2016 at 12:36:05PM +1100, David Gibson wrote: > > On Tue, Mar 15, 2016 at 10:08:56AM +0530, Bharata B Rao wrote: > > > Add support to hot remove pc-dimm memory devices. > > > > > > Signed-off-by: Bharata B Rao <[email protected]> > > > > Reviewed-by: David Gibson <[email protected]> > > > > Looks correct, but again, needs to wait on the PAPR change. [...] > > While we are here, I would also like to get some opinion on the real > need for memory unplug. Is there anything that memory unplug gives us > which memory ballooning (shrinking mem via ballooning) can't give ? Sure ballooning can complement memory hotplug but turning it on would effectively reduce hotplug to balloning as it would enable overcommit capability instead of hard partitioning pc-dimms provides. So one could just use ballooning only and not bother with hotplug at all. On the other hand memory hotplug/unplug (at least on x86) tries to model real hardware, thus removing need in paravirt ballooning solution in favor of native guest support. PS: Guest wise, currently hot-unplug is not well supported in linux, i.e. it's not guarantied that guest will honor unplug request as it may pin dimm by using it as a non migratable memory. So there is something to work on guest side to make unplug more reliable/guarantied. > > Regards, > Bharata. > >
