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 C0C9143F4B3 for ; Thu, 13 Aug 2026 10:00:39 +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=1786615240; cv=none; b=DiVgXJp4/gYC9USsEdaPq41V+wZ5oP31LbarEuoeg0GcKSnnCYw2cUpLLhmiTrpYmFfCkoGGPt3mXsG4vsl807be8Ybt1Xu/5/fEQ4JkWEKnQ+skniTzJvAPXRbWLNyyXXjlSpnXMXyWskMzQe80O0fnRuSQXEPzpe2iXzu5usk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786615240; c=relaxed/simple; bh=1sBz5kBUbHD4lcr/+x3tS9aUKMpp1pfIESpNSLH8CWg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XhP4bNiyUmdk7aiMQbQ9C5jIeRj17lBymPpakbgP8nLExjeHOjwDjvOGURm8U2xbJ5YbfppkkWzTWrnGsUXopoN+YvnDLh3lXp3TKb8VAoaUtV8buL4fO2i3ieJZ2piMhN7bCtoxzpqYTCFu3tW12epXPVg/6wDoFS+iP0ouPAY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NxcOvnqT; 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="NxcOvnqT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD9471F00A3A; Thu, 13 Aug 2026 10:00:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786615239; bh=Z6TCyAyinvBPmg6vnO4koIVYOjxW7RfC67mGsAHWs5M=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NxcOvnqTLqnucN77/ABpJZAyzChmV2Fi0KnuSgNaUtL4FtePQ3yk+d58dIAGltofZ Dfd/Fh0av3tGTeKX9OydBN5Bj+R5YNfOzC142oLSyP5J5U69MtfW3Yx+T9zpe7L3fm aJhWxlVnp9/UFO2sCbrT4sLwqiZQ4kUtVvrm499OTClhrhujcTKhfgbUGE1LKO490b L6nOOPQS99TvdKGENVdlLz6UlkBVfZ4FhxRjgaPHR32thskI0EYAC6E4Jyq7GotH3Q 924JlasleBvAcWDtIghuv7dwqABEXCC60y14aDpcCVLGR8Acdi2AYiBbPpio2pG1xq G4riMK/2ozqiA== Message-ID: <89837004-b5c9-4b59-b795-3b79005379af@kernel.org> Date: Thu, 13 Aug 2026 12:00:30 +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: [RFC PATCH 0/8] Introducte Reserved THP To: Zi Yan , Qi Zheng , akpm@linux-foundation.org, ljs@kernel.org, baolin.wang@linux.alibaba.com, liam@infradead.org, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, muchun.song@linux.dev, osalvador@suse.de, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, youngjun.park@lge.com, peterx@redhat.com, usama.arif@linux.dev, willy@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng 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 ... digging through old mail. > > You mean the reservation should be done via some file handle, like > memfd, so that it is easy to apply memory policies to determine where > reserved memory locates? > > For existing hugetlb reservation, there is no fine control, like NUMA, > or cgroup, of the reserved free memory. > > Is that what you mean above? I guess, it's all tricky. hugetlb reservation is a mess. We better not make similar mistakes with THPs. [...] >>> 3.6 Remove Hugetlb >>> ------------------ >>> >>> Once reserved THP can completely replace the existing functions of hugetlb, we >>> can gradually remove Hugetlb, leaving only one huge page management system in >>> the kernel. >> >> I'm sorry, but no way this will work in any reasonable timeframe unless you >> mimic the exact user facing ABI -- and I don't think we'll gain a lot that way. >> >> I know, we all like to dream, but this just isn't feasible. > > Based on my understanding, the key takeway is that we want to have more > control over reserved memory, where to get the free memory, who gets how > much of the reserved memory, and more. yes, it's all very complicated. Slapping on some MADV_RESERVED_THP is just entirely the wrong way to tackle this. -- Cheers, David