From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 00D563E95A8 for ; Fri, 2 Oct 2026 19:13:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790968425; cv=none; b=uH0+iScZMzI+fnUpozcCy/H+srFbLVrBmT/pjvz7an4n2wvxidIGQfdieq7OdEbrFKL3lw0UNwFSzM4tYke4feh62zOQxjIQrcRuk4PiBSYQppYiBUXt+F3mGqzNX6g5jdYPC2pT1UThuty5s7+BYr4XDeuQO90fE7naF1iIC8c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790968425; c=relaxed/simple; bh=f0FVcabn2xBOPItNkVnvMaerPMKGYx822nHLBoO6YOM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=g/HdggR0YKafZgsQfKJNbKxZUqymVnAv8uxaOt9T+XI0D9+evuPCG2eGM7EoLevkgm3P4ojlnwQrxZLwx+EOCPEyGzokMAGm/IBGR+lBEhCTfpHVDu5+YaFatLJotgKcfobMFfMnlP53Rk1QqPq2bYJDsE7439RzyVI7shMMOiM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=K9RGZLcR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="K9RGZLcR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DB291F000FF; Fri, 2 Oct 2026 19:13:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790968423; bh=N56IVrkHgW95DKN/ml8uLc48V5Z4iV1gTSdArvZ350Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=K9RGZLcRaXo+mqMqoQm19xpxnkGstJ/aZ5hXngDTeNDvN6RovymJE4t2itC8nPsQJ a3bfVEBCUE4emwvTPlhMe3KP5iRBVZxu0QlL9XC0JUQDen/72NX5+I3YXPvrNbx5xs haBASBqJWmjtu13BwaK0vLrug7ai0w5HFxa+bYKVx4S6CufGr3xJwjPyxrJTG8prml YQe4mT0M6EY+4vPh4iNe2kCmHkOWf1xKA7cl4IfonUaIv1VrFS6Whm5RLUFruxN5fr o/ELjG5GpCRkvalZpf+/n695zoMolhY/CEblsAjRzxXiNaNHHuVgfe2WRq/rHK9tyX nHhDQHSVeQCaQ== Message-ID: <62d8b799-7e06-4060-ada8-62fb4633b124@kernel.org> Date: Fri, 2 Oct 2026 21:13:33 +0200 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 03/14] mm: introduce pgtable_has_pmd_leaves() To: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.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, 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: From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/18/26 03:45, Luiz Capitulino wrote: > Currently, we have two helpers that check for PMD-sized pages but have > different names and slightly different semantics: > > - has_transparent_hugepage(): the name suggests it checks if THP is > enabled, but when CONFIG_TRANSPARENT_HUGEPAGE=y and the architecture > implements this helper, it actually checks if the CPU supports > PMD-sized pages > > - thp_disabled_by_hw(): the name suggests it checks if THP is disabled > by the hardware, but it just returns a cached value acquired with > has_transparent_hugepage() during boot. This helper is used in fast > paths > > A better design would be to separate CONFIG_TRANSPARENT_HUGEPAGE > checking, which can be done with the IS_ENABLED() macro, from checking > if a CPU supports PMD-sized pages. > > To this end, this commit introduces a new helper called > pgtable_has_pmd_leaves() which offers the following advantages: > > 1. Well defined and clear semantics: it returns true if the CPU > supports PMD-sized pages and false otherwise > 2. It always returns a cached value, so it can be used in fast paths > 3. It's implemented with a static key: it's a no-op for archs not > implemeting it and for archs implementing it the static key is > changed only during boot > > The new helper requires an initialization step which is performed by > pgtable_leaf_support_init(). We call pgtable_leaf_support_init() early > during boot from mm_core_init(). > > The next commits will convert users of both has_transparent_hugepage() > and thp_disabled_by_hw() to pgtable_has_pmd_leaves() and/or > IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE). > > Signed-off-by: Luiz Capitulino > --- Clean, thanks Acked-by: David Hildenbrand (Arm) -- Cheers, David