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 92DFD2DF14A for ; Thu, 6 Nov 2025 21:29:21 +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=1762464563; cv=none; b=CDLpLK0SeJl5q+oneYzHrr1h7QR8g5tpCupix5E2+vxg8EEHnSIpYtR9EulfRFdUDjQb3q92M4dKyk/HXppvpdxewOewFtFRpgA1Zjz0aoB4hG8lG6HJL7MxkgQWpRTiisV3i2Zd0LjX3I3KS+OY22x9q1dCVCVGJGZ4WDLb/7A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762464563; c=relaxed/simple; bh=fmMPx+nIE9R0eDvKMK0buO9dC4R4qwFjkjuZ9muvTuo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=JPrdTbi7dFyeJS0agODj2PjN95U/gaG6caoWxXZWVCItJgQUk68N/QSmDw5gbBQtnCvWgAAA9AllHYQWnxgxKCa4xorVetKSibGXjcO+OFPomMmkPWCtLDbg2IfdwUXeQ6szT876/Te2Zls/Vfokksm/gYm875eEVqLyjZOg0XY= 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=EB4I/SS2; 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="EB4I/SS2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762464560; 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; bh=bfwhX0idL+jcT4fehCnbdNH5+2W0J91n2IFBGm3eZ6c=; b=EB4I/SS2HQOHNlA6VzIfesqrhMk7WHiqMgi/daeESRsG1Imi+/iCFIivoQMoKj03OkG8+w oAgLSrOnes430o2/5KeD75Z9l+7Y+pj+wBc8ABSA7oyJHbjEPZHSxvfNtrGO0uoV2WyHm2 Rf/F6iUyoc3+tOn60CHp+KIAdok79jM= 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-652-iBqmsrqeMyW0bHI0o7um3Q-1; Thu, 06 Nov 2025 16:29:16 -0500 X-MC-Unique: iBqmsrqeMyW0bHI0o7um3Q-1 X-Mimecast-MFC-AGG-ID: iBqmsrqeMyW0bHI0o7um3Q_1762464555 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 C4A801956063; Thu, 6 Nov 2025 21:29:14 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.65.101]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 8F25819560A7; Thu, 6 Nov 2025 21:29:13 +0000 (UTC) From: Luiz Capitulino To: david@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: ryan.roberts@arm.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Subject: [RFC 00/10] mm: thp: always enable mTHP support Date: Thu, 6 Nov 2025 16:28:47 -0500 Message-ID: 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 3.0 on 10.30.177.12 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 support. 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. An important detail is that we need to do the same refactoring for has_transparent_pud_hugepage(). I actually have patches for this one too, I'm not including them here because I want to get some initial feedback on the general approach first (and maybe it's better to do that in a separate series). Thanks to David Hildenbrand for suggesting this improvement and for providing guidance (all bugs and misconcentpions are mine). Luiz Capitulino (10): docs: tmpfs: remove implementation detail reference mm: introduce pgtable_has_pmd_leaves() drivers: dax: use pgtable_has_pmd_leaves() drivers: i915 selftest: use pgtable_has_pmd_leaves() drivers: nvdimm: use pgtable_has_pmd_leaves() mm: debug_vm_pgtable: use pgtable_has_pmd_leaves() treewide: rename has_transparent_hugepage() to arch_has_pmd_leaves() mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves() mm: thp: always enable mTHP support mm: thp: x86: cleanup PSE feature bit usage 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 | 6 ------ arch/x86/include/asm/pgtable_32.h | 6 ++++++ drivers/dax/dax-private.h | 2 +- .../gpu/drm/i915/gem/selftests/huge_pages.c | 2 +- drivers/nvdimm/pfn_devs.c | 4 ++-- include/linux/huge_mm.h | 7 ------- include/linux/pgtable.h | 14 +++++++++++-- mm/debug_vm_pgtable.c | 20 +++++++++---------- mm/huge_memory.c | 13 ++++++------ mm/memory.c | 12 ++++++++++- mm/shmem.c | 8 ++++---- 20 files changed, 72 insertions(+), 59 deletions(-) -- 2.51.1