Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [RFC PATCH] mm, hotplug: get rid of auto_online_blocks | Date | Mon, 27 Feb 2017 12:50:19 +0100 |
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Heiko Carstens <heiko.carstens@de.ibm.com> writes:
> 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.
Sorry, obviously missed 'x86' in the above statement.
> > 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. >
This is actually a very good example of why we need the config option. s390 kernels will have it disabled.
-- Vitaly
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