From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "peterx@redhat.com" <peterx@redhat.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: James Houghton <jthoughton@google.com>,
David Hildenbrand <david@redhat.com>,
Yang Shi <shy828301@gmail.com>,
Andrew Jones <andrew.jones@linux.dev>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Jason Gunthorpe <jgg@nvidia.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Rik van Riel <riel@surriel.com>,
John Hubbard <jhubbard@nvidia.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Vlastimil Babka <vbabka@suse.cz>,
Lorenzo Stoakes <lstoakes@gmail.com>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
Mike Rapoport <rppt@kernel.org>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH v3 00/12] mm/gup: Unify hugetlb, part 2
Date: Mon, 25 Mar 2024 14:56:41 +0000 [thread overview]
Message-ID: <e0c324e1-8dd1-4329-bcf4-56f7311aedcc@csgroup.eu> (raw)
In-Reply-To: <20240321220802.679544-1-peterx@redhat.com>
Le 21/03/2024 à 23:07, peterx@redhat.com a écrit :
> From: Peter Xu <peterx@redhat.com>
>
> v3:
> - Rebased to latest mm-unstalbe (a824831a082f, of March 21th)
> - Dropped patch to introduce pmd_thp_or_huge(), replace such uses (and also
> pXd_huge() users) with pXd_leaf() [Jason]
> - Add a comment for CONFIG_PGTABLE_HAS_HUGE_LEAVES [Jason]
> - Use IS_ENABLED() in follow_huge_pud() [Jason]
> - Remove redundant none pud check in follow_pud_mask() [Jason]
>
> rfc: https://lore.kernel.org/r/20231116012908.392077-1-peterx@redhat.com
> v1: https://lore.kernel.org/r/20231219075538.414708-1-peterx@redhat.com
> v2: https://lore.kernel.org/r/20240103091423.400294-1-peterx@redhat.com
>
> The series removes the hugetlb slow gup path after a previous refactor work
> [1], so that slow gup now uses the exact same path to process all kinds of
> memory including hugetlb.
>
> For the long term, we may want to remove most, if not all, call sites of
> huge_pte_offset(). It'll be ideal if that API can be completely dropped
> from arch hugetlb API. This series is one small step towards merging
> hugetlb specific codes into generic mm paths. From that POV, this series
> removes one reference to huge_pte_offset() out of many others.
>
> One goal of such a route is that we can reconsider merging hugetlb features
> like High Granularity Mapping (HGM). It was not accepted in the past
> because it may add lots of hugetlb specific codes and make the mm code even
> harder to maintain. With a merged codeset, features like HGM can hopefully
> share some code with THP, legacy (PMD+) or modern (continuous PTEs).
>
> To make it work, the generic slow gup code will need to at least understand
> hugepd, which is already done like so in fast-gup. Due to the specialty of
> hugepd to be software-only solution (no hardware recognizes the hugepd
> format, so it's purely artificial structures), there's chance we can merge
> some or all hugepd formats with cont_pte in the future. That question is
> yet unsettled from Power side to have an acknowledgement. As of now for
> this series, I kept the hugepd handling because we may still need to do so
> before getting a clearer picture of the future of hugepd. The other reason
> is simply that we did it already for fast-gup and most codes are still
> around to be reused. It'll make more sense to keep slow/fast gup behave
> the same before a decision is made to remove hugepd.
>
It is not true that hugepd is a software-only solution. Powerpc 8xx HW
matches the hugepd topology for 8M pages.
Christophe
prev parent reply other threads:[~2024-03-25 14:59 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-21 22:07 [PATCH v3 00/12] mm/gup: Unify hugetlb, part 2 peterx
2024-03-21 22:07 ` [PATCH v3 01/12] mm/Kconfig: CONFIG_PGTABLE_HAS_HUGE_LEAVES peterx
2024-03-21 22:07 ` [PATCH v3 02/12] mm/hugetlb: Declare hugetlbfs_pagecache_present() non-static peterx
2024-03-21 22:07 ` [PATCH v3 03/12] mm: Make HPAGE_PXD_* macros even if !THP peterx
2024-03-22 17:14 ` SeongJae Park
2024-03-23 0:30 ` Peter Xu
2024-03-23 1:05 ` SeongJae Park
2024-03-21 22:07 ` [PATCH v3 04/12] mm: Introduce vma_pgtable_walk_{begin|end}() peterx
2024-03-22 12:27 ` Jason Gunthorpe
2024-03-21 22:07 ` [PATCH v3 05/12] mm/gup: Drop folio_fast_pin_allowed() in hugepd processing peterx
2024-03-22 12:28 ` Jason Gunthorpe
2024-03-21 22:07 ` [PATCH v3 06/12] mm/gup: Refactor record_subpages() to find 1st small page peterx
2024-03-21 22:07 ` [PATCH v3 07/12] mm/gup: Handle hugetlb for no_page_table() peterx
2024-03-21 22:07 ` [PATCH v3 08/12] mm/gup: Cache *pudp in follow_pud_mask() peterx
2024-03-21 22:07 ` [PATCH v3 09/12] mm/gup: Handle huge pud for follow_pud_mask() peterx
2024-03-21 22:08 ` [PATCH v3 10/12] mm/gup: Handle huge pmd for follow_pmd_mask() peterx
2024-03-21 22:08 ` [PATCH v3 11/12] mm/gup: Handle hugepd for follow_page() peterx
2024-03-21 22:08 ` [PATCH v3 12/12] mm/gup: Handle hugetlb in the generic follow_page_mask code peterx
2024-03-22 13:30 ` Jason Gunthorpe
2024-03-22 15:55 ` Peter Xu
2024-03-22 16:08 ` Jason Gunthorpe
2024-03-22 20:48 ` Andrew Morton
2024-03-23 0:45 ` Peter Xu
2024-03-23 2:15 ` Peter Xu
2024-03-22 16:10 ` [PATCH v3 00/12] mm/gup: Unify hugetlb, part 2 Jason Gunthorpe
2024-03-25 18:58 ` Peter Xu
2024-03-26 14:02 ` Jason Gunthorpe
2024-04-04 21:48 ` Peter Xu
2024-04-05 18:16 ` Jason Gunthorpe
2024-04-05 21:42 ` Peter Xu
2024-04-09 23:43 ` Jason Gunthorpe
2024-04-10 15:28 ` Peter Xu
2024-04-10 16:30 ` Christophe Leroy
2024-04-10 19:58 ` Peter Xu
2024-04-12 14:27 ` Christophe Leroy
2024-03-25 14:56 ` Christophe Leroy [this message]
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