From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Luiz Capitulino <luizcap@redhat.com>,
Usama Arif <usama.arif@linux.dev>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
baolin.wang@linux.alibaba.com, ziy@nvidia.com,
lance.yang@linux.dev
Cc: corbet@lwn.net, tsbogend@alpha.franken.de, maddy@linux.ibm.com,
mpe@ellerman.id.au, agordeev@linux.ibm.com,
gerald.schaefer@linux.ibm.com, hca@linux.ibm.com,
gor@linux.ibm.com, x86@kernel.org, tglx@kernel.org,
mingo@redhat.com, bp@alien8.de, hughd@google.com,
dave.hansen@linux.intel.com, djbw@kernel.org,
vishal.l.verma@intel.com, dave.jiang@intel.com,
akpm@linux-foundation.org, yintirui@huawei.com, dev.jain@arm.com
Subject: Re: [PATCH v8 00/14] mm: thp: always enable mTHP support
Date: Fri, 18 Sep 2026 22:23:06 +0200 [thread overview]
Message-ID: <cfd9c86f-26e3-4914-b148-8202b942e5c6@kernel.org> (raw)
In-Reply-To: <970c8f34-3cf4-4c6c-931c-b132e3bc6838@redhat.com>
On 9/18/26 16:01, Luiz Capitulino wrote:
>
>
> On 9/18/26 6:37 AM, Usama Arif wrote:
>>
>>
>> On 18/09/2026 02:45, Luiz Capitulino wrote:
>>> Introduction
>>> ============
>>>
>>> Today, if an architecture implements has_transparent_hugepage() and the CPU
>>> lacks support for PMD-sized pages, the THP code disables all THP, including
>>> mTHP.
>>
>>
>> Hi Luiz,
>>
>> Sorry for asking this so late in the series, but which CPUs lack support for
>> PMD sized pages?
>>
>> Is this series mainly for PowerPC?
>
> No :)
>
> The architectures that have conditional PMD page support (ie. discovered
> at run-time via has_transparent_hugepage()) are x86, s390, powerpc and
> mips.
>
> For x86 for example, even on 64-bit there are cases where the PSE bit
> may not be present (eg. some errata and by hypervisor CPUID masking).
>
> That being said, the main goal of the series is that
> has_transparent_hugepage() is overloaded: it has different semantics on
> those architectures and is used to gate all THP support (which is not
> the right thing to do for mTHP).
Yes, and I hope that we can then follow-up with similar PUD support cleanup to
rework some of that CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD magic.
--
Cheers,
David
prev parent reply other threads:[~2026-09-18 20:23 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-18 1:45 Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 01/14] docs: tmpfs: remove implementation detail reference Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 02/14] mm: shmem: shmem_getattr(): set blksize to highest supported THP order Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 03/14] mm: introduce pgtable_has_pmd_leaves() Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 04/14] drivers: dax: use pgtable_has_pmd_leaves() Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 05/14] drivers: nvdimm: " Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 06/14] mm: debug_vm_pgtable: " Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 07/14] mm: shmem: allow THP support determination at folio allocation time Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 08/14] s390: move has_transparent_hugepage() out of THP guard Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 09/14] powerpc: " Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 10/14] mips: " Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 11/14] x86: " Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 12/14] treewide: introduce arch_has_pmd_leaves() Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 13/14] mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves() Luiz Capitulino
2026-09-18 1:45 ` [PATCH v8 14/14] mm: thp: always enable mTHP support Luiz Capitulino
2026-09-18 9:01 ` Baolin Wang
2026-09-18 10:37 ` [PATCH v8 00/14] " Usama Arif
2026-09-18 14:01 ` Luiz Capitulino
2026-09-18 20:23 ` David Hildenbrand (Arm) [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cfd9c86f-26e3-4914-b148-8202b942e5c6@kernel.org \
--to=david@kernel.org \
--cc=agordeev@linux.ibm.com \
--cc=akpm@linux-foundation.org \
--cc=baolin.wang@linux.alibaba.com \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=dave.jiang@intel.com \
--cc=dev.jain@arm.com \
--cc=djbw@kernel.org \
--cc=gerald.schaefer@linux.ibm.com \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=hughd@google.com \
--cc=lance.yang@linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luizcap@redhat.com \
--cc=maddy@linux.ibm.com \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=tglx@kernel.org \
--cc=tsbogend@alpha.franken.de \
--cc=usama.arif@linux.dev \
--cc=vishal.l.verma@intel.com \
--cc=x86@kernel.org \
--cc=yintirui@huawei.com \
--cc=ziy@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®