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Tue, 10 Feb 2026 05:28:27 -0800 (PST) X-Received: by 2002:ac8:7f55:0:b0:4ee:c1a:f11f with SMTP id d75a77b69052e-506399e4b33mr199812401cf.84.1770730107444; Tue, 10 Feb 2026 05:28:27 -0800 (PST) Received: from [192.168.2.110] ([76.65.77.217]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8caf9fdfa1bsm1047769185a.45.2026.02.10.05.28.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Feb 2026 05:28:27 -0800 (PST) Message-ID: <0c0886d5-2561-40e4-94e9-6fca15f25127@redhat.com> Date: Tue, 10 Feb 2026 08:28:16 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 10/11] mm: thp: always enable mTHP support To: Baolin Wang , 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: <29e8dfc2772af4b6e0db24134ca3563ec422b91a.1770675272.git.luizcap@redhat.com> From: Luiz Capitulino In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: aN9DsbBSsvDyNinglysF7JEAljJL8S3vxLa2Mmleeeg_1770730108 X-Mimecast-Originator: redhat.com Content-Language: en-US, en-CA Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 6529F1C0018 X-Rspamd-Server: rspam07 X-Stat-Signature: n9wxhkhhu5eq5sdtoqwf4zoa8o7m1nzn X-HE-Tag: 1770730114-299307 X-HE-Meta: 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 tUXxZzek LDD08z65fUAZIXeDARrJ3IMz/wIPxjdKuYeJ0xMK67uTP9RmXvKHP6bLfkVzgSPiX9Lq/BYLZPhpjGVTlNZW91NqUclLWN9rpmDIfCPs+1TXLqcdnhyqTTIBgMbK2eWyCJKksN1wVyLZypaiWay3Carid/O5UWyJyk23iZXaUR2hHxoVl0VxDCQz1X+a0Wo2xwxKkQBV0ktakDNA3afV0mNqtPpy5D6yvPbJTZBBURTcBC9fbjMMuuBhzcLfaORliyqB9nZu2BnNbztIpbrWSXxugJPDYSBo6WlZ1ESvwlQM6R1Sq11CyaSgVAfYdmH4oESrjpfFQRH6YB/m/lRfU2PjtHbLqLL7Wd7N4NTVbMf13pnFlefg3mY3ymSv/z4ZzQOCAFMnWc/D5mWMnTNjJkEG5Gp3AChNOzHuM X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-02-10 04:56, Baolin Wang wrote: > > > On 2/10/26 6:14 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 | 11 +++++++---- >> mm/shmem.c | 4 +++- >> 2 files changed, 10 insertions(+), 5 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 1e5ea2e47f79..882331592928 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -115,6 +115,9 @@ 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; >> @@ -122,7 +125,7 @@ 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. */ >> @@ -806,6 +809,9 @@ 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)); > > I think you should also handle the 'huge_anon_orders_inherit' setting in this function if pgtable_has_pmd_leaves() returns false. Shmem as well. > > if (!anon_orders_configured) > huge_anon_orders_inherit = BIT(PMD_ORDER); Good catch. So, would you agree that should set it to BIT(PMD_ORDER - 1) in this case? > >> + >> order = highest_order(orders); >> while (orders) { >> thpsize = thpsize_create(order, *hugepage_kobj); >> @@ -905,9 +911,6 @@ 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 1c98e84667a4..cb325d1e2d1e 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -1827,7 +1827,7 @@ 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, >> @@ -1935,6 +1935,8 @@ 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)); > > Moving this check into shmem_allowable_huge_orders() would be more appropriate. Will do. Thanks a lot for the very fast review. > >> if (orders > 0) { >> suitable_orders = shmem_suitable_orders(inode, vmf, >