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

[Michal Hocko]

On Thu 23-02-17 17:36:38, Vitaly Kuznetsov wrote:
> Michal Hocko <mhocko at kernel.org> writes:
[...]
> > Is a grow from 256M -> 128GB really something that happens in real life?
> > Don't get me wrong but to me this sounds quite exaggerated. Hotmem add
> > which is an operation which has to allocate memory has to scale with the
> > currently available memory IMHO.
> 
> With virtual machines this is very real and not exaggerated at
> all. E.g. Hyper-V host can be tuned to automatically add new memory when
> guest is running out of it. Even 100 blocks can represent an issue.

Do you have any reference to a bug report. I am really curious because
something really smells wrong and it is not clear that the chosen
solution is really the best one.
[...]
> > Because the udev will run a code which can cope with that - retry if the
> > error is recoverable or simply report with all the details. Compare that
> > to crawling the system log to see that something has broken...
> 
> I don't know much about udev, but the most common rule to online memory
> I've met is:
> 
> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline",  ATTR{state}="online"
> 
> doesn't do anything smart.

So what? Is there anything that prevents doing something smarter?
-- 
Michal Hocko
SUSE Labs