On 21.10.19 17:47, Michal Hocko wrote:
On Mon 21-10-19 17:39:36, David Hildenbrand wrote:
On 21.10.19 16:43, Michal Hocko wrote:
[...]
We still set PageReserved before onlining pages and that one should be
good to go as well (memmap_init_zone).
Thanks!
memmap_init_zone() is called when onlining memory. There, set all pages to
reserved right now (on context == MEMMAP_HOTPLUG). We clear PG_reserved when
onlining a page to the buddy (e.g., generic_online_page). If we would online
a memory block with holes, we would want to keep all such pages
(!pfn_valid()) set to reserved. Also, there might be other side effects.
Isn't it sufficient to have those pages in a poisoned state? They are
not onlined so their state is basically undefined anyway. I do not see
how PageReserved makes this any better.
It is what people have been using for a long time. Memory hole ->
PG_reserved. The memmap is valid, but people want to tell "this here is
crap, don't look at it".
Also is the hole inside a hotplugable memory something we really have to
care about. Has anybody actually seen a platform to require that?
That's what I was asking. I can see "support" for this was added
basically right from the beginning. I'd say we rip that out and
cleanup/simplify. I am not aware of a platform that requires this.
Especially, memory holes on DIMMs (detected during boot) seem like an
unlikely thing.
--
Thanks,
David / dhildenb
