On Mon 27-02-17 12:25:10, Heiko Carstens wrote: > On Mon, Feb 27, 2017 at 11:02:09AM +0100, Vitaly Kuznetsov wrote: > > A couple of other thoughts: > > 1) Having all newly added memory online ASAP is probably what people > > want for all virtual machines. > > This is not true for s390. On s390 we have "standby" memory that a guest > sees and potentially may use if it sets it online. Every guest that sets > memory offline contributes to the hypervisor's standby memory pool, while > onlining standby memory takes memory away from the standby pool. > > The use-case is that a system administrator in advance knows the maximum > size a guest will ever have and also defines how much memory should be used > at boot time. The difference is standby memory. > > Auto-onlining of standby memory is the last thing we want. > > > Unfortunately, we have additional complexity with memory zones > > (ZONE_NORMAL, ZONE_MOVABLE) and in some cases manual intervention is > > required. Especially, when further unplug is expected. > > This also is a reason why auto-onlining doesn't seem be the best way. Can you imagine any situation when somebody actually might want to have this knob enabled? From what I understand it doesn't seem to be the case. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
