From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@suse.com>, Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <songmuchun@bytedance.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm: Make alloc_contig_range handle free hugetlb pages
Date: Wed, 17 Feb 2021 14:36:47 +0100 [thread overview]
Message-ID: <182f6a4a-6f95-9911-7730-8718ab72ece2@redhat.com> (raw)
In-Reply-To: <YC0agxVWYRKGm5IO@dhcp22.suse.cz>
On 17.02.21 14:30, Michal Hocko wrote:
> On Wed 17-02-21 11:08:15, Oscar Salvador wrote:
>> Free hugetlb pages are tricky to handle so as to no userspace application
>> notices disruption, we need to replace the current free hugepage with
>> a new one.
>>
>> In order to do that, a new function called alloc_and_dissolve_huge_page
>> is introduced.
>> This function will first try to get a new fresh hugetlb page, and if it
>> succeeds, it will dissolve the old one.
>>
>> With regard to the allocation, since we do not know whether the old page
>> was allocated on a specific node on request, the node the old page belongs
>> to will be tried first, and then we will fallback to all nodes containing
>> memory (N_MEMORY).
>
> I do not think fallback to a different zone is ok. If yes then this
> really requires a very good reasoning. alloc_contig_range is an
> optimistic allocation interface at best and it shouldn't break carefully
> node aware preallocation done by administrator.
What does memory offlining do when migrating in-use hugetlbfs pages?
Does it always keep the node?
I think keeping the node is the easiest/simplest approach for now.
>
>> Note that gigantic hugetlb pages are fenced off since there is a cyclic
>> dependency between them and alloc_contig_range.
>
> Why do we need/want to do all this in the first place?
cma and virtio-mem (especially on ZONE_MOVABLE) really want to handle
hugetlbfs pages.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-02-17 13:41 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 10:08 [PATCH 0/2] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-02-17 10:08 ` [PATCH 1/2] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
2021-02-17 13:30 ` Michal Hocko
2021-02-17 13:36 ` David Hildenbrand [this message]
2021-02-17 13:50 ` Michal Hocko
2021-02-17 13:53 ` David Hildenbrand
2021-02-17 13:59 ` Michal Hocko
2021-02-17 14:08 ` David Hildenbrand
2021-02-17 14:14 ` Michal Hocko
2021-02-17 14:23 ` Oscar Salvador
2021-02-17 13:42 ` Oscar Salvador
2021-02-17 15:00 ` Michal Hocko
2021-02-18 10:09 ` Oscar Salvador
2021-02-18 12:52 ` Michal Hocko
2021-02-18 13:32 ` Oscar Salvador
2021-02-18 13:59 ` Michal Hocko
2021-02-18 16:53 ` Oscar Salvador
2021-02-19 9:05 ` Oscar Salvador
2021-02-19 9:56 ` Michal Hocko
2021-02-19 10:14 ` Oscar Salvador
2021-02-19 20:00 ` Mike Kravetz
2021-02-19 10:40 ` Oscar Salvador
2021-02-19 10:55 ` Michal Hocko
2021-02-19 11:17 ` Oscar Salvador
2021-02-19 11:24 ` Michal Hocko
2021-02-17 10:08 ` [PATCH 2/2] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-02-17 13:36 ` Michal Hocko
2021-02-17 13:46 ` Oscar Salvador
2021-02-17 13:54 ` Michal Hocko
2021-02-17 15:06 ` Michal Hocko
2021-02-17 15:27 ` Oscar Salvador
2021-02-17 15:33 ` Michal Hocko
2021-02-18 6:01 ` Oscar Salvador
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