Re: [PATCH 1/1] mm/memory_hotplug: Adds option to hot-add memory in ZONE_MOVABLE

[Leonardo Bras <leonardo@linux.ibm.com>]

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On Thu, 2019-07-18 at 08:19 -0400, Pavel Tatashin wrote:
> On Wed, Jul 17, 2019 at 10:42 PM Leonardo Bras <leonardo@linux.ibm.com> wrote:
> > Adds an option on kernel config to make hot-added memory online in
> > ZONE_MOVABLE by default.
> > 
> > This would be great in systems with MEMORY_HOTPLUG_DEFAULT_ONLINE=y by
> > allowing to choose which zone it will be auto-onlined
> 
> This is a desired feature. From reading the code it looks to me that
> auto-selection of online method type should be done in
> memory_subsys_online().
> 
> When it is called from device online, mem->online_type should be -1:
> 
> if (mem->online_type < 0)
>      mem->online_type = MMOP_ONLINE_KEEP;
> 
> Change it to:
> if (mem->online_type < 0)
>      mem->online_type = MMOP_DEFAULT_ONLINE_TYPE;
> 
> And in "linux/memory_hotplug.h"
> #ifdef CONFIG_MEMORY_HOTPLUG_MOVABLE
> #define MMOP_DEFAULT_ONLINE_TYPE MMOP_ONLINE_MOVABLE
> #else
> #define MMOP_DEFAULT_ONLINE_TYPE MMOP_ONLINE_KEEP
> #endif
> 
> Could be expanded to support MMOP_ONLINE_KERNEL as well.
> 
> Pasha

Thanks for the suggestions Pasha,

I was made aware there is a kernel boot option "movable_node" that
already creates the behavior I was trying to reproduce.

I was thinking of changing my patch in order to add a config option
that makes this behavior default (i.e. not need to pass it as a boot
parameter.

Do you think that it would still be a desired feature?

Regards,

Leonardo Brás

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