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Howlett" , ryan.roberts@arm.com, Vlastimil Babka , 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 Message-ID: References: <20260630164143.1595669-1-usama.arif@linux.dev> <20260630164143.1595669-7-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2ECFF4000B X-Stat-Signature: nu13tkrbm5a1swkaqjakcniuar7t1wu7 X-Rspam-User: X-HE-Tag: 1783011327-80169 X-HE-Meta: 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 drFgh3EI AI0mGbd43JV35gXI/foXXme7imPoxQYpeb1YHSMhgl0AvO8HNYg9Y+b0QE/o1TYmrGGTCY/dF1SnMT/bMaeV3wOnCvt13h/eIgMFMOTOyHE9YdsY4dH0kOgUJeTrBT2J0YfGtJdlvwY991Jxy2clylnNDJO5oEdgmviQTP9jpGEO3cl+pdwP+NwacYS1dyZdtx/U78f3xj7DLLaa51P7p4C/axrRwQIXcHp2GtYZfxjZ6mRe1pwqlDdUyXXbfqKSvlsnCIjehzEVYwD4RaKZ2yFm75eeJnJ6zRJe+wQWfXBGN+B0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jul 01, 2026 at 10:03:21PM +0200, 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 :) ). > > So yeah, renaming the config option makes sense. The config space is the wild west. > > We have > > PGTABLE_HAS_HUGE_LEAVES > > and stuff like > > HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD > HAVE_ARCH_SOFT_DIRTY > ARCH_HAS_GIGANTIC_PAGE > ARCH_HAS_PTE_SPECIAL > > We do have a limited number of "SUPPORTS" (which is longer than HAS), but I > would either use > > > ARCH_HAS_PMD_SOFTLEAVES > > or > > HAVE_ARCH_PMD_SOFTLEAVES Yeah it'd be GREAT to simplify all this! > > > Apart from that LGTM. Can I just say I love this patch in general though? Softleaf all the things :)) > > -- > Cheers, > > David Cheers, Lorenzo