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From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Souptick Joarder <jrdr.linux@gmail.com>,
	linux-hyperv@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Oscar Salvador <osalvador@suse.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>, Qian Cai <cai@lca.pw>,
	Sasha Levin <sashal@kernel.org>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Yang <richard.weiyang@gmail.com>
Subject: Re: [PATCH v1 0/3] mm/memory_hotplug: Export generic_online_page()
Date: Mon, 23 Sep 2019 14:34:23 +0200	[thread overview]
Message-ID: <8203a264-b327-d512-32ee-054214d2b883@redhat.com> (raw)
In-Reply-To: <20190923123008.GP6016@dhcp22.suse.cz>

On 23.09.19 14:30, Michal Hocko wrote:
> On Mon 23-09-19 14:20:05, David Hildenbrand wrote:
>> On 23.09.19 14:07, Michal Hocko wrote:
>>> On Mon 23-09-19 13:34:18, David Hildenbrand wrote:
>>>> On 23.09.19 13:15, Michal Hocko wrote:
>>> [...]
>>>>> I am wondering why those pages get onlined when they are, in fact,
>>>>> supposed to be offline.
>>>>>
>>>>
>>>> It's the current way of emulating sub-memory-block hotplug on top of the
>>>> memory bock device API we have. Hyper-V and XEN have been using that for
>>>> a long time.
>>>
>>> Do they really have to use the existing block interface when they in
>>> fact do not operate on the block granularity? Zone device memory already
>>> acts on sub section/block boundaries.
>>>
>>
>> Yes, we need memory blocks, especially for user space to properly online
>> them (as we discussed a while back, to decide on a zone) and for udev
>> events, to e.g., properly reload kexec when memory blocks get
>> added/removed/onlined/offlined.
> 
> Just to make sure I really follow. We need a user interface to control
> where the memory gets onlined but it is the driver which determines
> which part of the block really gets onlined, right?
> 

Yes, it's the drivers job to decide which part of the memory block can
actually get used, and when.

It's a little bit like the driver immediately allocates unbacked memory
again, to free that memory to the buddy once requested. (similar to how
ballooning works).

-- 

Thanks,

David / dhildenb

      reply	other threads:[~2019-09-23 12:34 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09 11:48 [PATCH v1 0/3] mm/memory_hotplug: Export generic_online_page() David Hildenbrand
2019-09-09 11:48 ` [PATCH v1 1/3] " David Hildenbrand
2019-09-09 11:48 ` [PATCH v1 2/3] hv_balloon: Use generic_online_page() David Hildenbrand
2019-09-09 11:48 ` [PATCH v1 3/3] mm/memory_hotplug: Remove __online_page_free() and __online_page_increment_counters() David Hildenbrand
2019-09-20  8:17 ` [PATCH v1 0/3] mm/memory_hotplug: Export generic_online_page() David Hildenbrand
2019-09-23  8:58   ` Michal Hocko
2019-09-23  9:31     ` David Hildenbrand
2019-09-23 11:15       ` Michal Hocko
2019-09-23 11:34         ` David Hildenbrand
2019-09-23 11:43           ` David Hildenbrand
2019-09-23 12:07           ` Michal Hocko
2019-09-23 12:20             ` David Hildenbrand
2019-09-23 12:30               ` Michal Hocko
2019-09-23 12:34                 ` David Hildenbrand [this message]

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