Re: [PATCH v2 0/8] mm/memory_hotplug: allow to specify a default online_type

Michal Hocko
2020-03-18T13:54:15Z

On Wed 18-03-20 21:05:17, Baoquan He wrote:
> On 03/17/20 at 11:49am, David Hildenbrand wrote:
> > Distributions nowadays use udev rules ([1] [2]) to specify if and
> > how to online hotplugged memory. The rules seem to get more complex with
> > many special cases. Due to the various special cases,
> > CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE cannot be used. All memory hotplug
> > is handled via udev rules.
> >
> > Everytime we hotplug memory, the udev rule will come to the same
> > conclusion. Especially Hyper-V (but also soon virtio-mem) add a lot of
> > memory in separate memory blocks and wait for memory to get onlined by user
> > space before continuing to add more memory blocks (to not add memory faster
> > than it is getting onlined). This of course slows down the whole memory
> > hotplug process.
> >
> > To make the job of distributions easier and to avoid udev rules that get
> > more and more complicated, let's extend the mechanism provided by
> > - /sys/devices/system/memory/auto_online_blocks
> > - "memhp_default_state=" on the kernel cmdline
> > to be able to specify also "online_movable" as well as "online_kernel"
>
> This patch series looks good, thanks. Since Andrew has merged it to -mm again,
> I won't add my Reviewed-by to bother.

JFYI, Andrew usually adds R-b or A-b tags as they are posted.

--
Michal Hocko
SUSE Labs