Re: [PATCH] arm64: configurable sparsemem section size

[Michal Hocko]

On Tue 23-04-19 16:38:43, Pavel Tatashin wrote:
> sparsemem section size determines the maximum size and alignment that
> is allowed to offline/online memory block. The bigger the size the less
> the clutter in /sys/devices/system/memory/*. On the other hand, however,
> there is less flexability in what granules of memory can be added and
> removed.
> 
> Recently, it was enabled in Linux to hotadd persistent memory that
> can be either real NV device, or reserved from regular System RAM
> and has identity of devdax.
> 
> The problem is that because ARM64's section size is 1G, and devdax must
> have 2M label section, the first 1G is always missed when device is
> attached, because it is not 1G aligned.
> 
> Allow, better flexibility by making section size configurable.

Is there any inherent reason (64k page size?) that enforces such a large
memsection?
-- 
Michal Hocko
SUSE Labs