Subject: Re: [RFC PATCH] memory-hotplug: Use dev_online for memhp_auto_offline

From: Vitaly Kuznetsov <[email-masked]>
Date: Fri, 24 Feb 2017 17:40:25 +0100

Michal Hocko <[email-masked]> writes:

> On Fri 24-02-17 17:09:13, Vitaly Kuznetsov wrote:

>> I have a smal  guest and I want to add more memory to it and the
>> result is ... OOM. Not something I expected.
>
> Which is not all that unexpected if you use a technology which has to
> allocated in order to add more memory.
>

My point is: why should users care about this? It's our problem that we
can't always hotplug memory. And I think this problem is solvable.

>> 
>> While this will most probably work for me I still disagree with the
>> concept of 'one size fits all' here and the default 'false' for ACPI,
>> we're taking away the feature from KVM/Vmware folks so they'll again
>> come up with the udev rule which has known issues.
>
> Well, AFAIU acpi_memory_device_add is a standard way how to announce
> physical memory added to the system. Where does the KVM/VMware depend on
> this to do memory ballooning?

As far as I understand memory hotplug in KVM/VMware is pure ACPI memory
hotplug, there is no specific code for it.

-- 
  Vitaly