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Fri, 1 May 2026 19:20:26 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.64.126]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id EECEF1800480; Fri, 1 May 2026 19:20:23 +0000 (UTC) From: Luiz Capitulino To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.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, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Subject: [PATCH v4 9/9] mm: thp: always enable mTHP support Date: Fri, 1 May 2026 15:18:51 -0400 Message-ID: In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-MFC-PROC-ID: wlhwLMJcysbfYGzN0DIB4wsAqBLkvR1_C29C2yslclE_1777663227 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C2E71140005 X-Stat-Signature: 34fxqeiihsieppj7fpe3ezur34ikeins X-Rspam-User: X-HE-Tag: 1777663233-673046 X-HE-Meta: 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 112Jgmjv 3JmrdeEar14nkCX3oc7s5k/Jrjs0F1E1dDJd3SF3GijXF+S75MGdMn3gVfZr5dq5x4nalWIOYBiq0eSxnJVAv5xUsQjx8lRJG/Y2BuYi9+XX7p7fHi/M44WNC0RasI8JaBJRFEFtoTZhFYUN/me3djgbtd5uRxNZkOaeXzIhujJVMHFxB0lneN1pZqU+yLZa8gbu5jQx6ALLaKMcD+BPlVmeW7c8RrX+hRIC8qnubMRebb64KV4/Fze16P233sxiv5H693CA4PV7o/6q7ATLxLY/VDvZGINcK2ZbIH2WgoK5ObnhnZtMyRVuYwvPGlPiXh5plKrbuQZqHt1m4cei3BQnbHg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: If PMD-sized pages are not supported on an architecture (ie. the arch implements arch_has_pmd_leaves() and it returns false) then the current code disables all THP, including mTHP. This commit fixes this by allowing mTHP to be always enabled for all archs. When PMD-sized pages are not supported, its sysfs entry won't be created and their mapping will be disallowed at page-fault time. Similarly, this commit implements the following changes for shmem in shmem_allowable_huge_orders(): - Drop the pgtable_has_pmd_leaves() check so that mTHP sizes are considered - Filter out PMD and PUD orders from allowable orders when PMD-sized pages are not supported by the CPU Signed-off-by: Luiz Capitulino --- mm/huge_memory.c | 23 ++++++++++++++++++----- mm/shmem.c | 14 +++++++++----- 2 files changed, 27 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 32254febe097..c1765c8e3dc6 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -126,6 +126,14 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, else supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; + if (!pgtable_has_pmd_leaves()) { + /* + * The CPU doesn't support PMD-sized pages, assume it + * doesn't support PUD-sized pages either. + */ + supported_orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); + } + orders &= supported_orders; if (!orders) return 0; @@ -133,7 +141,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, if (!vma->vm_mm) /* vdso */ return 0; - if (!pgtable_has_pmd_leaves() || vma_thp_disabled(vma, vm_flags, forced_collapse)) + if (vma_thp_disabled(vma, vm_flags, forced_collapse)) return 0; /* khugepaged doesn't collapse DAX vma, but page fault is fine. */ @@ -848,7 +856,7 @@ static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) * disable all other sizes. powerpc's PMD_ORDER isn't a compile-time * constant so we have to do this here. */ - if (!anon_orders_configured) + if (!anon_orders_configured && pgtable_has_pmd_leaves()) huge_anon_orders_inherit = BIT(PMD_ORDER); *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); @@ -870,6 +878,14 @@ static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) } orders = THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE_DEFAULT; + if (!pgtable_has_pmd_leaves()) { + /* + * The CPU doesn't support PMD-sized pages, assume it + * doesn't support PUD-sized pages either. + */ + orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); + } + order = highest_order(orders); while (orders) { thpsize = thpsize_create(order, *hugepage_kobj); @@ -969,9 +985,6 @@ static int __init hugepage_init(void) int err; struct kobject *hugepage_kobj; - if (!pgtable_has_pmd_leaves()) - return -EINVAL; - /* * hugepages can't be allocated by the buddy allocator */ diff --git a/mm/shmem.c b/mm/shmem.c index a48f034830cd..23893c2bc2dd 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1840,16 +1840,19 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, unsigned long mask = READ_ONCE(huge_shmem_orders_always); unsigned long within_size_orders = READ_ONCE(huge_shmem_orders_within_size); vm_flags_t vm_flags = vma ? vma->vm_flags : 0; - unsigned int global_orders; + unsigned int global_orders, filter_orders = 0; - if (!pgtable_has_pmd_leaves() || (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force))) + if (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force)) return 0; + if (!pgtable_has_pmd_leaves()) + filter_orders = BIT(PMD_ORDER) | BIT(PUD_ORDER); + global_orders = shmem_huge_global_enabled(inode, index, write_end, shmem_huge_force, vma, vm_flags); /* Tmpfs huge pages allocation */ if (!vma || !vma_is_anon_shmem(vma)) - return global_orders; + return global_orders & ~filter_orders; /* * Following the 'deny' semantics of the top level, force the huge @@ -1863,7 +1866,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, * means non-PMD sized THP can not override 'huge' mount option now. */ if (shmem_huge == SHMEM_HUGE_FORCE) - return READ_ONCE(huge_shmem_orders_inherit); + return READ_ONCE(huge_shmem_orders_inherit) & ~filter_orders; /* Allow mTHP that will be fully within i_size. */ mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0); @@ -1874,6 +1877,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, if (global_orders > 0) mask |= READ_ONCE(huge_shmem_orders_inherit); + mask &= ~filter_orders; return THP_ORDERS_ALL_FILE_DEFAULT & mask; } @@ -5457,7 +5461,7 @@ void __init shmem_init(void) * Default to setting PMD-sized THP to inherit the global setting and * disable all other multi-size THPs. */ - if (!shmem_orders_configured) + if (!shmem_orders_configured && pgtable_has_pmd_leaves()) huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER); #endif return; -- 2.53.0