From: Michal Hocko <mhocko@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>,
akpm@linux-foundation.org, dan.j.williams@intel.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 2/2] mm, memory_hotplug: provide a more generic restrictions for memory hotplug
Date: Fri, 5 Apr 2019 12:30:53 +0200 [thread overview]
Message-ID: <20190405103053.GO12864@dhcp22.suse.cz> (raw)
In-Reply-To: <a4230528-dc7e-e17c-c363-e3da7961dbf1@redhat.com>
On Fri 05-04-19 10:05:09, David Hildenbrand wrote:
> On 05.04.19 09:14, Michal Hocko wrote:
> > On Thu 04-04-19 20:27:41, David Hildenbrand wrote:
> >> On 04.04.19 20:01, Oscar Salvador wrote:
> > [...]
> >>> But I am not really convinced by MHP_SYSTEM_RAM name, and I think we should stick
> >>> with MHP_MEMBLOCK_API because it represents __what__ is that flag about and its
> >>> function, e.g: create memory block devices.
> >
> > Exactly
>
> Fine with me for keeping what Oscar has.
>
> >
> >> This nicely aligns with the sub-section memory add support discussion.
> >>
> >> MHP_MEMBLOCK_API immediately implies that
> >>
> >> - memory is used as system ram. Memory can be onlined/offlined. Markers
> >> at sections indicate if the section is online/offline.
> >
> > No there is no implication like that. It means only that the onlined
> > memory has a sysfs interface. Nothing more, nothing less
>
> As soon as there is a online/offline interface, you *can* (and user
> space usually *will*) online that memory. Onlining/offlining is only
> defined for memory to be added to the buddy - memory to be used as
> "system ram". Doing it for random device memory will not work / result
> in undefined behavior.
No, not really. We really do not care where the memory comes from. Is it
RAM, NVDIMM, $FOO_BAR_OF_A_FUTURE_BUZZ. We only do care that the memory
can be onlined - user triggered associated with a zone. The memory even
doesn't have to go to the page allocator.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-04-05 10:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-04 12:59 [PATCH 0/2] Preparing memhotplug for allocating memmap from hot-added range Oscar Salvador
2019-04-04 12:59 ` [PATCH 1/2] mm, memory_hotplug: cleanup memory offline path Oscar Salvador
2019-04-04 13:18 ` David Hildenbrand
2019-04-04 13:25 ` Oscar Salvador
2019-04-04 14:47 ` David Hildenbrand
2019-04-04 15:40 ` Oscar Salvador
2019-04-04 16:50 ` David Hildenbrand
2019-04-04 12:59 ` [PATCH 2/2] mm, memory_hotplug: provide a more generic restrictions for memory hotplug Oscar Salvador
2019-04-04 14:57 ` David Hildenbrand
2019-04-04 15:02 ` David Hildenbrand
2019-04-04 18:01 ` Oscar Salvador
2019-04-04 18:27 ` David Hildenbrand
2019-04-05 7:14 ` Michal Hocko
2019-04-05 8:05 ` David Hildenbrand
2019-04-05 10:30 ` Michal Hocko [this message]
2019-04-05 10:56 ` David Hildenbrand
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