Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore for percent

[Michal Hocko]

On Mon 12-02-18 16:24:25, David Rientjes wrote:
> Both kernelcore= and movablecore= can be used to define the amount of
> ZONE_NORMAL and ZONE_MOVABLE on a system, respectively.  This requires
> the system memory capacity to be known when specifying the command line,
> however.
> 
> This introduces the ability to define both kernelcore= and movablecore=
> as a percentage of total system memory.  This is convenient for systems
> software that wants to define the amount of ZONE_MOVABLE, for example, as
> a proportion of a system's memory rather than a hardcoded byte value.
> 
> To define the percentage, the final character of the parameter should be
> a '%'.

I do not have any objections regarding the extension. What I am more
interested in is _why_ people are still using this command line
parameter at all these days. Why would anybody want to introduce lowmem
issues from 32b days. I can see the CMA/Hotplug usecases for
ZONE_MOVABLE but those have their own ways to define zone movable. I was
tempted to simply remove the kernelcore already. Could you be more
specific what is your usecase which triggered a need of an easier
scaling of the size?
-- 
Michal Hocko
SUSE Labs