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

Baoquan He
2020-03-18T14:42:04Z

On 03/18/20 at 02:54pm, Michal Hocko wrote:
> 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.

Got it, thanks for telling.