From: Zi Yan <ziy@nvidia.com>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Usama Arif <usama.arif@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org,
linux-mm@kvack.org, ying.huang@linux.alibaba.com,
Baoquan He <baoquan.he@linux.dev>,
willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org,
riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr,
kas@kernel.org, baohua@kernel.org, dev.jain@arm.com,
baolin.wang@linux.alibaba.com, npache@redhat.com,
"Liam R. Howlett" <liam@infradead.org>,
ryan.roberts@arm.com, Vlastimil Babka <vbabka@kernel.org>,
lance.yang@linux.dev, linux-kernel@vger.kernel.org,
nphamcs@gmail.com, shikemeng@huaweicloud.com,
kernel-team@meta.com
Subject: Re: [PATCH 6/6] mm: rename ARCH_ENABLE_THP_MIGRATION to ARCH_SUPPORTS_PMD_SOFTLEAF
Date: Wed, 01 Jul 2026 16:39:16 -0400 [thread overview]
Message-ID: <AB2F36E5-2040-4C73-A049-E10DBB6BF035@nvidia.com> (raw)
In-Reply-To: <e37df165-8de0-4924-ba19-0d43a6b7d36e@kernel.org>
On 1 Jul 2026, at 16:03, David Hildenbrand (Arm) wrote:
> On 6/30/26 18:34, Usama Arif wrote:
>> CONFIG_ARCH_ENABLE_THP_MIGRATION started life gating just PMD-level
>> migration entries, but has grown to gate the entire PMD-level softleaf
>> machinery: migration entries, device-private entries, and soon swap
>> entries.
>
> device-private really relies on migration support.
>
> See do_huge_pmd_device_private() where we migrate back to CPU memory.
>
> The whole concept is pased on migration. So that's why it currently makes sense.
>
> So "has grown to" is not quite accurate. It's a different story with swap
> entries (that can exist even without migration support).
>
>
>> Rename CONFIG_ARCH_ENABLE_THP_MIGRATION to CONFIG_ARCH_SUPPORTS_PMD
>> _SOFTLEAF to make this clear. This is a pure rename: the set of
>> selecting architectures (x86, arm64, s390, riscv, loongarch, and
>> powerpc on PPC_BOOK3S_64) and the gating semantics are unchanged.
>
> Hm, that makes me wonder what it would take to make this all just be implicitly
> supported by CONFIG_TRANSPARENT_HUGEPAGE.
>
> Looks like someone would have the courage to touch stuff like arc, mips and
> sparc64 (+arm and x86, but that's less of a concern :) ).
You mean me back in 2018[1]? ;)
At least I got a no go for s390.
[1] https://lore.kernel.org/linux-mm/20180426142804.180152-1-zi.yan@sent.com/
Best Regards,
Yan, Zi
next prev parent reply other threads:[~2026-07-01 20:39 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-30 16:34 [PATCH 0/6] mm: preparatory patches for PMD level swap entries Usama Arif
2026-06-30 16:34 ` [PATCH 1/6] mm: add softleaf_to_pmd() and convert existing callers Usama Arif
2026-07-03 10:21 ` Lance Yang
2026-06-30 16:34 ` [PATCH 2/6] mm: extract mm_prepare_for_swap_entries() helper Usama Arif
2026-07-01 16:56 ` David Hildenbrand (Arm)
2026-06-30 16:34 ` [PATCH 3/6] fs/proc: use softleaf_has_pfn() in pagemap PMD walker Usama Arif
2026-06-30 16:34 ` [PATCH 4/6] mm/huge_memory: move softleaf_to_folio() inside migration branch Usama Arif
2026-06-30 16:34 ` [PATCH 5/6] mm/migrate_device: move softleaf_to_folio() inside device-private branch Usama Arif
2026-07-01 19:40 ` David Hildenbrand (Arm)
2026-06-30 16:34 ` [PATCH 6/6] mm: rename ARCH_ENABLE_THP_MIGRATION to ARCH_SUPPORTS_PMD_SOFTLEAF Usama Arif
2026-07-01 20:03 ` David Hildenbrand (Arm)
2026-07-01 20:39 ` Zi Yan [this message]
2026-07-01 20:50 ` David Hildenbrand (Arm)
2026-07-01 20:55 ` Zi Yan
2026-07-02 16:55 ` Lorenzo Stoakes
2026-06-30 19:50 ` [PATCH 0/6] mm: preparatory patches for PMD level swap entries Andrew Morton
2026-07-01 8:04 ` Lorenzo Stoakes
2026-07-01 23:46 ` Andrew Morton
2026-07-02 10:48 ` Lorenzo Stoakes
2026-07-02 13:08 ` Mike Rapoport
2026-07-02 16:53 ` Lorenzo Stoakes
2026-07-02 16:57 ` Mark Brown
2026-07-02 17:08 ` Lorenzo Stoakes
2026-07-02 17:10 ` David Hildenbrand (Arm)
2026-07-02 17:21 ` Lorenzo Stoakes
2026-07-03 19:45 ` SJ Park
2026-07-04 10:04 ` Mike Rapoport
2026-07-05 21:10 ` SJ Park
2026-07-01 10:44 ` Usama Arif
2026-07-01 14:09 ` Usama Arif
2026-07-01 20:04 ` David Hildenbrand (Arm)
2026-07-03 17:48 ` Usama Arif
2026-07-05 1:31 ` Andrew Morton
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