From: Rik van Riel <riel@surriel.com>
To: David Hildenbrand <david@redhat.com>, Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>, Roman Gushchin <guro@fb.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
linux-mm@kvack.org,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
Shakeel Butt <shakeelb@google.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
David Nellans <dnellans@nvidia.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 00/16] 1GB THP support on x86_64
Date: Wed, 09 Sep 2020 09:49:08 -0400 [thread overview]
Message-ID: <4923e178c12f38148a2620ba31fcded349e555fb.camel@surriel.com> (raw)
In-Reply-To: <6135d2c5-2a74-6ca8-4b3b-8ceb25c0d4b1@redhat.com>
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On Wed, 2020-09-09 at 15:43 +0200, David Hildenbrand wrote:
> On 09.09.20 15:19, Rik van Riel wrote:
> > On Wed, 2020-09-09 at 09:04 +0200, Michal Hocko wrote:
> >
> > > That CMA has to be pre-reserved, right? That requires a
> > > configuration.
> >
> > To some extent, yes.
> >
> > However, because that pool can be used for movable
> > 4kB and 2MB
> > pages as well as for 1GB pages, it would be easy to just set
> > the size of that pool to eg. 1/3 or even 1/2 of memory for every
> > system.
> >
> > It isn't like the pool needs to be the exact right size. We
> > just need to avoid the "highmem problem" of having too little
> > memory for kernel allocations.
> >
>
> I am not sure I like the trend towards CMA that we are seeing,
> reserving
> huge buffers for specific users (and eventually even doing it
> automatically).
>
> What we actually want is ZONE_MOVABLE with relaxed guarantees, such
> that
> anybody who requires large, unmovable allocations can use it.
>
> I once played with the idea of having ZONE_PREFER_MOVABLE, which
> a) Is the primary choice for movable allocations
> b) Is allowed to contain unmovable allocations (esp., gigantic pages)
> c) Is the fallback for ZONE_NORMAL for unmovable allocations, instead
> of
> running out of memory
>
> If someone messes up the zone ratio, issues known from zone
> imbalances
> are avoided - large allocations simply become less likely to succeed.
> In
> contrast to ZONE_MOVABLE, memory offlining is not guaranteed to work.
I really like that idea. This will be easier to deal with than
a "just the right size" CMA area, and seems like it would be
pretty forgiving in both directions.
Keeping unmovable allocations
contained to one part of memory
should also make compaction within the ZONE_PREFER_MOVABLE area
a lot easier than compaction for higher order allocations is
today.
I suspect your proposal solves a lot of issues at once.
For (c) from your proposal, we could even claim a whole
2MB or even 1GB area at once for unmovable allocations,
keeping those contained in a limited amount of physical
memory again, to make life easier on compaction.
--
All Rights Reversed.
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next prev parent reply other threads:[~2020-09-09 13:49 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-02 18:06 [RFC PATCH 00/16] 1GB THP support on x86_64 Zi Yan
2020-09-02 18:06 ` [RFC PATCH 01/16] mm: add pagechain container for storing multiple pages Zi Yan
2020-09-02 20:29 ` Randy Dunlap
2020-09-02 20:48 ` Zi Yan
2020-09-03 3:15 ` Matthew Wilcox
2020-09-07 12:22 ` Kirill A. Shutemov
2020-09-07 15:11 ` Zi Yan
2020-09-09 13:46 ` Kirill A. Shutemov
2020-09-09 14:15 ` Zi Yan
2020-09-02 18:06 ` [RFC PATCH 02/16] mm: thp: 1GB anonymous page implementation Zi Yan
2020-09-02 18:06 ` [RFC PATCH 03/16] mm: proc: add 1GB THP kpageflag Zi Yan
2020-09-09 13:46 ` Kirill A. Shutemov
2020-09-02 18:06 ` [RFC PATCH 04/16] mm: thp: 1GB THP copy on write implementation Zi Yan
2020-09-02 18:06 ` [RFC PATCH 05/16] mm: thp: handling 1GB THP reference bit Zi Yan
2020-09-09 14:09 ` Kirill A. Shutemov
2020-09-09 14:36 ` Zi Yan
2020-09-02 18:06 ` [RFC PATCH 06/16] mm: thp: add 1GB THP split_huge_pud_page() function Zi Yan
2020-09-09 14:18 ` Kirill A. Shutemov
2020-09-09 14:19 ` Zi Yan
2020-09-02 18:06 ` [RFC PATCH 07/16] mm: stats: make smap stats understand PUD THPs Zi Yan
2020-09-02 18:06 ` [RFC PATCH 08/16] mm: page_vma_walk: teach it about PMD-mapped PUD THP Zi Yan
2020-09-02 18:06 ` [RFC PATCH 09/16] mm: thp: 1GB THP support in try_to_unmap() Zi Yan
2020-09-02 18:06 ` [RFC PATCH 10/16] mm: thp: split 1GB THPs at page reclaim Zi Yan
2020-09-02 18:06 ` [RFC PATCH 11/16] mm: thp: 1GB THP follow_p*d_page() support Zi Yan
2020-09-02 18:06 ` [RFC PATCH 12/16] mm: support 1GB THP pagemap support Zi Yan
2020-09-02 18:06 ` [RFC PATCH 13/16] mm: thp: add a knob to enable/disable 1GB THPs Zi Yan
2020-09-02 18:06 ` [RFC PATCH 14/16] mm: page_alloc: >=MAX_ORDER pages allocation an deallocation Zi Yan
2020-09-02 18:06 ` [RFC PATCH 15/16] hugetlb: cma: move cma reserve function to cma.c Zi Yan
2020-09-02 18:06 ` [RFC PATCH 16/16] mm: thp: use cma reservation for pud thp allocation Zi Yan
2020-09-02 18:40 ` [RFC PATCH 00/16] 1GB THP support on x86_64 Jason Gunthorpe
2020-09-02 18:45 ` Zi Yan
2020-09-02 18:48 ` Jason Gunthorpe
2020-09-02 19:05 ` Zi Yan
2020-09-02 19:57 ` Jason Gunthorpe
2020-09-02 20:29 ` Zi Yan
2020-09-03 16:40 ` Jason Gunthorpe
2020-09-03 16:55 ` Matthew Wilcox
2020-09-03 17:08 ` Jason Gunthorpe
2020-09-03 7:32 ` Michal Hocko
2020-09-03 16:25 ` Roman Gushchin
2020-09-03 16:50 ` Jason Gunthorpe
2020-09-03 17:01 ` Matthew Wilcox
2020-09-03 17:18 ` Jason Gunthorpe
2020-09-03 20:57 ` Mike Kravetz
2020-09-03 21:06 ` Roman Gushchin
2020-09-04 7:42 ` Michal Hocko
2020-09-04 21:10 ` Roman Gushchin
2020-09-07 7:20 ` Michal Hocko
2020-09-08 15:09 ` Zi Yan
2020-09-08 19:58 ` Roman Gushchin
2020-09-09 4:01 ` John Hubbard
2020-09-09 7:15 ` Michal Hocko
2020-09-03 14:23 ` Kirill A. Shutemov
2020-09-03 16:30 ` Roman Gushchin
2020-09-08 11:57 ` David Hildenbrand
2020-09-08 14:05 ` Zi Yan
2020-09-08 14:22 ` David Hildenbrand
2020-09-08 15:36 ` Zi Yan
2020-09-08 14:27 ` Matthew Wilcox
2020-09-08 15:50 ` Zi Yan
2020-09-09 12:11 ` Jason Gunthorpe
2020-09-09 12:32 ` Matthew Wilcox
2020-09-09 13:14 ` Jason Gunthorpe
2020-09-09 13:27 ` David Hildenbrand
2020-09-10 10:02 ` William Kucharski
2020-09-08 14:35 ` Michal Hocko
2020-09-08 14:41 ` Rik van Riel
2020-09-08 15:02 ` David Hildenbrand
2020-09-09 7:04 ` Michal Hocko
2020-09-09 13:19 ` Rik van Riel
2020-09-09 13:43 ` David Hildenbrand
2020-09-09 13:49 ` Rik van Riel [this message]
2020-09-09 13:54 ` David Hildenbrand
2020-09-10 7:32 ` Michal Hocko
2020-09-10 8:27 ` David Hildenbrand
2020-09-10 14:21 ` Zi Yan
2020-09-10 14:34 ` David Hildenbrand
2020-09-10 14:41 ` Zi Yan
2020-09-10 15:15 ` David Hildenbrand
2020-09-10 13:32 ` Rik van Riel
2020-09-10 14:30 ` Zi Yan
2020-09-09 13:59 ` Michal Hocko
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