From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 7E1D135A3B1 for ; Fri, 1 May 2026 19:20:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777663207; cv=none; b=XvBiu1ecrA5V/IfIdErTiInhNUqHEGe7FV3JukhQr5sPzzyCHgw4WreqM9tfWHm6BuzOcTpS9i10YY2tsvqB0l4SVapf8aPBkfFxLlruI1pAHDcH82YQR0aTZwWcPDJ/ZYQuR2/N4TA7zKiws9mEXuVS3CzHdeN5TpFEFxrTNV8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777663207; c=relaxed/simple; bh=mtrNiwtOsJAbK9Z0a2b0WvZm8rKTePnUZbS+Zt685lA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=U+rYHF9OGTkHAG/zUIVUKjI/gHs9ZDao+S1qcVCtY+sr8CZSWCaXBbGqwQF15Acr8w+RWrPYa5xhTLFXHNl+DZmIO/Bgz85+O3eFapOn8tIOPQcqrICzZY4jEnKYNH94jQVlttnEpdr15S7a19eO0kdW7vcCjT9aZRBn8/i0dZk= 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=J46kyCBr; arc=none smtp.client-ip=170.10.129.124 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="J46kyCBr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777663205; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=cY6LaFmqcqx3jjavRgihKIw3vSF+bJhM7Jxo3NBkAY0=; b=J46kyCBrOqZPITQ1+c14uB5NmdfJSQqzrblZ2pDENX5rr/TPlNtjzVN5ML1PF2a5c/YG0u Wu9oUi2zhWVCXkqZRBQ4VLh8PHP4hZXnOMNZhSAhWnMdww96bz0Te8YKgusjt7eH+hdWkW lgVzDDvICGee3H9wnF3KVnxgW6y0iAg= Received: from mx-prod-mc-03.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-599-gWRvNscCP3GXc_lH56B9Qg-1; Fri, 01 May 2026 15:19:59 -0400 X-MC-Unique: gWRvNscCP3GXc_lH56B9Qg-1 X-Mimecast-MFC-AGG-ID: gWRvNscCP3GXc_lH56B9Qg_1777663197 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 164D119560B7; Fri, 1 May 2026 19:19:56 +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 0A64C1801481; Fri, 1 May 2026 19:19:51 +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 0/9] mm: thp: always enable mTHP support Date: Fri, 1 May 2026 15:18:42 -0400 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Today, if an architecture implements has_transparent_hugepage() and the CPU lacks support for PMD-sized pages, the THP code disables all THP, including mTHP. In addition, the kernel lacks a well defined API to check for PMD-sized page support. It currently relies on has_transparent_hugepage() and thp_disabled_by_hw(), but they are not well defined and are tied to THP support. This series addresses both issues by introducing a new well defined API to query PMD-sized page support: pgtable_has_pmd_leaves(). Using this new helper, we ensure that mTHP remains enabled even when the architecture or CPU doesn't support PMD-sized pages. Thanks to David Hildenbrand for suggesting this improvement and for providing guidance (all bugs and misconceptions are mine). This applies to Linus tree 08d0d3466664 ("Merge tag 'net-7.1-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net") NOTE: I used Claude Code Opus 4.6 to *review* the series before posting. It did find one issue where a pgtable_has_pmd_leaves() check was missing when assining huge_shmem_orders_inherit in shmem_init(). v4 -- - Use static key for pgtable_has_pmd_leaves() API (Lance) - Moved shmem pgtable_has_pmd_leaves() check to shmem_allowable_huge_orders() (Baolin) - Default pgtable_has_pmd_leaves() implementation to IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE) (Zi) - Dropped patch “mm: thp: x86: cleanup PSE feature bit usage” (Dave) v3 -- - Rebased on top of latest Linus tree - Removed i915 patch as driver dropped has_transparent_hugepage() usage - Moved init_arch_has_pmd_leaves() call in start_kernel() to avoid conflict with early_param handlers clearing CPU feature flags - Fixed build error with CONFIG_MMU=n (kernel test robot) - Fixed huge_anon_orders_inherit default setting when !pgtable_pmd_leaves() (Baolin) - Small commit changelog improvements v2 -- - Added support for always enabling mTHPs for shmem (Baolin) - Improved commits changelog & added reviewed-by v1 -- - Call init_arch_has_pmd_leaves() from start_kernel() - Keep pgtable_has_pmd_leaves() calls tied to CONFIG_TRANSPARENT_HUGEPAGE (David) - Clear PUD_ORDER when clearing PMD_ORDER (David) - Small changelog improvements (David) - Rebased on top of latest mm-new Luiz Capitulino (9): docs: tmpfs: remove implementation detail reference mm: introduce pgtable_has_pmd_leaves() drivers: dax: use pgtable_has_pmd_leaves() drivers: nvdimm: use pgtable_has_pmd_leaves() mm: debug_vm_pgtable: use pgtable_has_pmd_leaves() mm: shmem: drop has_transparent_hugepage() usage treewide: introduce arch_has_pmd_leaves() mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves() mm: thp: always enable mTHP support Documentation/filesystems/tmpfs.rst | 5 ++-- arch/mips/include/asm/pgtable.h | 4 +-- arch/mips/mm/tlb-r4k.c | 4 +-- arch/powerpc/include/asm/book3s/64/hash-4k.h | 2 +- arch/powerpc/include/asm/book3s/64/hash-64k.h | 2 +- arch/powerpc/include/asm/book3s/64/pgtable.h | 10 ++++---- arch/powerpc/include/asm/book3s/64/radix.h | 2 +- arch/powerpc/mm/book3s64/hash_pgtable.c | 4 +-- arch/s390/include/asm/pgtable.h | 4 +-- arch/x86/include/asm/pgtable.h | 4 +-- drivers/dax/dax-private.h | 2 +- drivers/nvdimm/pfn_devs.c | 6 +++-- include/linux/huge_mm.h | 7 ------ include/linux/pgtable.h | 19 ++++++++++++-- init/main.c | 1 + mm/debug_vm_pgtable.c | 20 +++++++-------- mm/huge_memory.c | 25 +++++++++++++------ mm/memory.c | 11 +++++++- mm/shmem.c | 21 +++++++++------- 19 files changed, 93 insertions(+), 60 deletions(-) -- 2.53.0