From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 0BBED361DA0 for ; Fri, 1 May 2026 19:20:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777663235; cv=none; b=cEW9PF5ytDtYyMJYcMKONqK0qvarwc9TOtRM92dApUJj1nCNxNKjHAMMTtT/kxmCV+bPc8n0p5DBcLkGZ28/Qyov5f9eaYJ7pFT+ukB50LzH+yn9l3Ljm0/adwzKHsghyxrJlqqwv/rsjj2mIzH/GuvdAWf5wWvp8IuQfG9LfGM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777663235; c=relaxed/simple; bh=zTmmwtRW5eOUa0XVvzuHMct5Gy2vUp5HzUBqsMEMbs0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OkWQOrMDyztNBdNdAGiPQEB/08VUSnFzh3KWTpS/oQQ0QuSkv0BvQ6y9z2ICggzLJQ07o6U8mvfaAjOuoAHHKRqojMeGhN1qofEICZSQ3D+M5H3UsFSAy10WUjcylmVPLNRXtR0K/FUMqDUr8f9qBpzI2DBe1m/eDQYOHUVXJyQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=c49qXg+K; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="c49qXg+K" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777663233; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+8y7DwT1Mvod+Su8a9kqNPeVGjZgNT6OWk7sX0RRnCo=; b=c49qXg+KefWG/wAcmfPdlw81XQ/+wo7CS8fhgJHlsIG7aEhkVGXtF2sTMZKiQlMdNqhP+o AtdBn0N9++WpP+aZ+wVKFC6rlWXwt+qciKR+JiGmAe97HUddWi3mtV9avqqWhjT6IpixNE Z1PpYRXc3PKt7+0CzVmK6QmtAYubas8= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-102-xmOm1cvmMIS1ApbmwSCO1w-1; Fri, 01 May 2026 15:20:29 -0400 X-MC-Unique: xmOm1cvmMIS1ApbmwSCO1w-1 X-Mimecast-MFC-AGG-ID: xmOm1cvmMIS1ApbmwSCO1w_1777663227 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BBEC5195608B; 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: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 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