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b=woAEs/Np3B1hIAgoNhkE7wwR7aVyFH4ZIv0dn9sjf7xt/Q+njnYD9/oSv/1UbwT/BzdNXy2qT0KuCmFvMfi5OEfRXh/ZxdV8AaTfXwXAzsk2+dg5Mcj8jbIQ35qQGbC6jVnYUPwCTgYbNPEz2MHTnTmMMm7z0VCXri9FG1yIOHU= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037026112;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0X0n6158_1775892131; Received: from 30.74.144.103(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X0n6158_1775892131 cluster:ay36) by smtp.aliyun-inc.com; Sat, 11 Apr 2026 15:22:12 +0800 Message-ID: <5e653a9b-9265-4bfd-89ce-f0fbe0df2ae6@linux.alibaba.com> Date: Sat, 11 Apr 2026 15:22:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 09/10] mm: thp: always enable mTHP support To: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org Cc: ryan.roberts@arm.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com References: <6dea717fe8c86003e7da33c9a7623b834649d5ee.1775679721.git.luizcap@redhat.com> From: Baolin Wang In-Reply-To: <6dea717fe8c86003e7da33c9a7623b834649d5ee.1775679721.git.luizcap@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6306E40004 X-Stat-Signature: ndxjg1qdiboj9w3ceepicwfn7mktbum7 X-Rspam-User: X-HE-Tag: 1775892136-418401 X-HE-Meta: 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 gLmXrS6b Bm2t48YT3zDwTgqi8u7U8vKRKS3zzDJYMzKqxX/6KAmiVmaYixgf+qZo1IGtVHELdIzfW3U6rX2A7P6bvb6CBBzG07AmJXIfGE1E5nghFPLcYV2F3hftT+1iOmAVjMNeSZMGSBYyhpIKqW95uWLNcObAykWnSg4h3aac1c4fh7FzIsUeMsVaYv+JFwDWenO3em+/QeXA1FmxC+ypmLKyB0/b2BIbsEiw1vlac3V8GodtaYb/ZqETPDQ0X0Uv26blPTpT7ChmTM75YdTAyYC5hoPX0A3KaeX8ck2Np58n84Iba9No= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/9/26 4:23 AM, Luiz Capitulino wrote: > 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 > - In shmem_alloc_and_add_folio(): don't consider PMD and PUD orders > when PMD-sized pages are not supported by the CPU > > Signed-off-by: Luiz Capitulino > --- > mm/huge_memory.c | 13 ++++++++----- > mm/shmem.c | 4 +++- > 2 files changed, 11 insertions(+), 6 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 86e489c0a150..6de3d8ebc35c 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -118,6 +118,9 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, > else > supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; > > + if (!pgtable_has_pmd_leaves()) > + supported_orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); > + > orders &= supported_orders; > if (!orders) > return 0; > @@ -125,7 +128,7 @@ 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. */ > @@ -787,7 +790,7 @@ 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); > @@ -809,6 +812,9 @@ 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()) > + orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); > + > order = highest_order(orders); > while (orders) { > thpsize = thpsize_create(order, *hugepage_kobj); > @@ -908,9 +914,6 @@ 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 613393eae5a9..b49a30475cb0 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1839,7 +1839,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, > vm_flags_t vm_flags = vma ? vma->vm_flags : 0; > unsigned int global_orders; > > - 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; > > global_orders = shmem_huge_global_enabled(inode, index, write_end, > @@ -1947,6 +1947,8 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf, > > if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > orders = 0; > + else if (!pgtable_has_pmd_leaves()) > + orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); Sorry, I still don't like the changes here, because shmem_allowable_huge_orders() is meant to determine which large orders are allowed. Something like below (untested): @@ -1834,6 +1834,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, struct vm_area_struct *vma, pgoff_t index, loff_t write_end, bool shmem_huge_force) { + unsigned int filter_orders = pgtable_has_pmd_leaves() ? (BIT(PMD_ORDER) | BIT(PUD_ORDER)) : 0; 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; @@ -1846,7 +1847,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, 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 @@ -1871,6 +1872,7 @@ 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; } Additionally, we also need a pgtable_has_pmd_leaves() check before setting huge_shmem_orders_inherit as well. @@ -5428,7 +5430,7 @@ 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;