From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 588CB1E520A for ; Thu, 8 Oct 2026 02:08:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.110 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791425290; cv=none; b=huIDatPc5XL7ZgEdGhKCSckp1iKhpG+YhS/SC/mI3ptVMzWPktDMkNTjqp63A634HaEekGmtAwA23SgolEIMTNfKq4Cktwv6a26tQVqmDSq125THMb2eZCMZitRR2yQAsN2u9wNd9mnM/L67M6VfMY7IY997yRs2qMWME3Fyw5o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791425290; c=relaxed/simple; bh=vqTFX+JYbuXr/EHlmJH8RY0+qPOMgiNPl66ttW+XRbI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ABITBOhLwKPf2+4NYcouu5HlwV/19ledNgAKQHPl5owrgVd7b//VD+my93hp4RTwn3Vgsv1/Vv/XNAtiHFQndyYsLMz336qDb6j7F2QvSHCI+G0oM73VxoC/Iz5WKQnLQm97AUU1KKwjGAEgSmAE3wJcRtu8sK5GUvU7C1YavN4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=f+CUJzz8; arc=none smtp.client-ip=115.124.30.110 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="f+CUJzz8" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1791425279; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=ODRL+vWaVDz42U2hwyZZZW2Lci6L6eJHWxbCTbwo0Bg=; b=f+CUJzz8a3do2c6s9gQaX44Cbq47dj+lZ+S5rnwXzVNMHy2+wntTYpt+2zr2llr7uDnooGTSV1EluEwsZATJuuH3s3fVjHQ52nOe3L/A2w34P/mgMkvwRrC3f5YkkI/ZzJSo91CSJuAB029xoubOPxbl9kgf5oet6hgbmOAcTyE= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045133197;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=27;SR=0;TI=SMTPD_---0XCIdo11_1791425276; Received: from 30.74.144.149(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XCIdo11_1791425276 cluster:ay36) by smtp.aliyun-inc.com; Thu, 08 Oct 2026 10:07:57 +0800 Message-ID: <4db5fdee-4bca-43bf-8ded-2fd8808ac289@linux.alibaba.com> Date: Thu, 8 Oct 2026 10:07:56 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 14/14] mm: thp: always enable mTHP support To: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, 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, usama.arif@linux.dev References: <752f528f0fed5cdc9de12b54260b0495d4e5a6cb.1789695931.git.luizcap@redhat.com> From: Baolin Wang In-Reply-To: <752f528f0fed5cdc9de12b54260b0495d4e5a6cb.1789695931.git.luizcap@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/18/26 9:45 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 > - 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 | 25 ++++++++++++++++++++----- > mm/shmem.c | 14 +++++++++----- > 2 files changed, 29 insertions(+), 10 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index a06025b87e7c..a2d6de3ea988 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -189,6 +189,15 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, > else > supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; > > + if (!pgtable_has_pmd_leaves()) { > + /* > + * If the CPU does not support PMD leaves, assume for > + * now that it does not support PUD leaves and disable > + * both folio orders. > + */ > + supported_orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); > + } > + > orders &= supported_orders; > if (!orders) > return 0; > @@ -196,7 +205,7 @@ 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. */ > @@ -979,7 +988,7 @@ 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); > @@ -1001,6 +1010,15 @@ 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()) { > + /* > + * If the CPU does not support PMD leaves, assume for > + * now that it does not support PUD leaves and disable > + * both folio orders. > + */ > + orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); > + } > + > order = highest_order(orders); > while (orders) { > thpsize = thpsize_create(order, *hugepage_kobj); > @@ -1091,9 +1109,6 @@ 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 bc2de3a7c1ea..8c0f7e3efeeb 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2046,11 +2046,14 @@ 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, disabled_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()) > + disabled_orders = BIT(PMD_ORDER); > + > global_orders = shmem_huge_global_enabled(inode, index, write_end, > shmem_huge_force, vma, vm_flags); > /* > @@ -2058,7 +2061,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, > * sysfs configs. > */ > if (!vma || !vma_is_anon_shmem(vma) || shmem_huge_force) > - return global_orders; > + return global_orders & ~disabled_orders; If you move the 'disabled_orders' filtering logic into shmem_huge_global_enabled(), as I mentioned in patch 8, then this change can be removed. > /* > * Following the 'deny' semantics of the top level, force the huge > @@ -2072,7 +2075,7 @@ 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) & ~disabled_orders; Since you've already disabled PMD-sized and PUD-sized orders for the 'shmem_enabled' interface in hugepage_init_sysfs(), this change can also be dropped. > /* Allow mTHP that will be fully within i_size. */ > mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0); > @@ -2083,6 +2086,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, > if (global_orders > 0) > mask |= READ_ONCE(huge_shmem_orders_inherit); > > + mask &= ~disabled_orders; Ditto. > return THP_ORDERS_ALL_FILE_DEFAULT & mask; > }