From: Mike Kravetz <mike.kravetz@oracle.com>
To: Oscar Salvador <osalvador@suse.de>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, mhocko@suse.com, david@redhat.com
Subject: Re: [RFC PATCH] mm,memory_hotplug: Unlock 1GB-hugetlb on x86_64
Date: Wed, 27 Feb 2019 14:00:57 -0800 [thread overview]
Message-ID: <201cc8d8-953f-f198-bbfe-96470136db68@oracle.com> (raw)
In-Reply-To: <20190227215109.cpiaheyqs2qdbl7p@d104.suse.de>
On 2/27/19 1:51 PM, Oscar Salvador wrote:
> On Thu, Feb 21, 2019 at 10:42:12AM +0100, Oscar Salvador wrote:
>> [1] https://lore.kernel.org/patchwork/patch/998796/
>>
>> Signed-off-by: Oscar Salvador <osalvador@suse.de>
>
> Any further comments on this?
> I do have a "concern" I would like to sort out before dropping the RFC:
>
> It is the fact that unless we have spare gigantic pages in other notes, the
> offlining operation will loop forever (until the customer cancels the operation).
> While I do not really like that, I do think that memory offlining should be done
> with some sanity, and the administrator should know in advance if the system is going
> to be able to keep up with the memory pressure, aka: make sure we got what we need in
> order to make the offlining operation to succeed.
> That translates to be sure that we have spare gigantic pages and other nodes
> can take them.
>
> Given said that, another thing I thought about is that we could check if we have
> spare gigantic pages at has_unmovable_pages() time.
> Something like checking "h->free_huge_pages - h->resv_huge_pages > 0", and if it
> turns out that we do not have gigantic pages anywhere, just return as we have
> non-movable pages.
Of course, that check would be racy. Even if there is an available gigantic
page at has_unmovable_pages() time there is no guarantee it will be there when
we want to allocate/use it. But, you would at least catch 'most' cases of
looping forever.
> But I would rather not convulate has_unmovable_pages() with such checks and "trust"
> the administrator.
Agree
--
Mike Kravetz
next prev parent reply other threads:[~2019-02-27 22:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 9:42 [RFC PATCH] mm,memory_hotplug: Unlock 1GB-hugetlb on x86_64 Oscar Salvador
2019-02-21 22:12 ` Mike Kravetz
2019-02-22 8:24 ` Oscar Salvador
2019-02-27 21:51 ` Oscar Salvador
2019-02-27 22:00 ` Mike Kravetz [this message]
2019-02-28 7:38 ` David Hildenbrand
2019-02-28 9:16 ` Michal Hocko
2019-02-28 9:21 ` Michal Hocko
2019-02-28 9:41 ` Oscar Salvador
2019-02-28 9:55 ` Michal Hocko
2019-02-28 10:19 ` Oscar Salvador
2019-02-28 12:11 ` Michal Hocko
2019-02-28 13:40 ` Oscar Salvador
2019-02-28 14:08 ` Michal Hocko
2019-02-28 21:01 ` Oscar Salvador
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