From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Zi Yan <ziy@nvidia.com>
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, 1 Jul 2026 22:50:30 +0200 [thread overview]
Message-ID: <03395825-2455-4b9d-b1bb-4232738afb30@kernel.org> (raw)
In-Reply-To: <AB2F36E5-2040-4C73-A049-E10DBB6BF035@nvidia.com>
On 7/1/26 22:39, Zi Yan wrote:
> 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.
hah! and 8 years later it seems to exist upstream :)
commit 10dd5a0009898ba35eafeb6087e5c83b84742ff1
Author: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Date: Tue Jul 29 13:16:19 2025 +0200
s390/mm: Enable THP_SWAP and THP_MIGRATION
After hugetlbfs PTE_MARKER support for s390 introduced region-third and
segment table swap entries, it is now possible to also enable THP_SWAP
and THP_MIGRATION for s390.
So, with that out of the way, could you revive your patchset?
--
Cheers,
David
next prev parent reply other threads:[~2026-07-01 20:50 UTC|newest]
Thread overview: 18+ 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
2026-06-30 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
2026-07-01 20:50 ` David Hildenbrand (Arm) [this message]
2026-07-01 20:55 ` Zi Yan
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 10:44 ` Usama Arif
2026-07-01 14:09 ` Usama Arif
2026-07-01 20:04 ` David Hildenbrand (Arm)
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