Re: [PATCH v1 1/2] mm/page_alloc.c: Don't set pages PageReserved() when offlining

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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






[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux