Re: [PATCH 0/2] memory_hotplug: introduce config and command line options to set the default onlining policy

[David Rientjes]

On Wed, 6 Apr 2016, Andrew Morton wrote:

> > This patchset continues the work I started with:
> > 
> > commit 31bc3858ea3ebcc3157b3f5f0e624c5962f5a7a6
> > Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> > Date:   Tue Mar 15 14:56:48 2016 -0700
> > 
> >     memory-hotplug: add automatic onlining policy for the newly added memory
> > 
> > Initially I was going to stop there and bring the policy setting logic to
> > userspace. I met two issues on this way:
> > 
> > 1) It is possible to have memory hotplugged at boot (e.g. with QEMU). These
> >    blocks stay offlined if we turn the onlining policy on by userspace.
> > 
> > 2) My attempt to bring this policy setting to systemd failed, systemd
> >    maintainers suggest to change the default in kernel or ... to use tmpfiles.d
> >    to alter the policy (which looks like a hack to me): 
> >    https://github.com/systemd/systemd/pull/2938
> 
> That discussion really didn't come to a conclusion and I don't
> understand why you consider Lennert's "recommended way" to be a hack?
> 
> > Here I suggest to add a config option to set the default value for the policy
> > and a kernel command line parameter to make the override.
> 
> But the patchset looks pretty reasonable regardless of the above.
> 

I don't understand why initscripts simply cannot crawl sysfs memory blocks 
and online them for the same behavior.