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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92e6233a5acsm49235185a.35.2026.06.29.12.00.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Jun 2026 12:00:34 -0700 (PDT) Date: Mon, 29 Jun 2026 15:00:29 -0400 From: Gregory Price To: "David Hildenbrand (Arm)" Cc: Qi Zheng , akpm@linux-foundation.org, ljs@kernel.org, ziy@nvidia.com, 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, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng Subject: Re: [RFC PATCH 0/8] Introducte Reserved THP Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: fwjowt1c64c6xhify5ddodx538t5swy8 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6674940016 X-HE-Tag: 1782759636-380661 X-HE-Meta: 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 /6gzNaMj CfEeOjSb5qbwejQrN7vRXd5Iir5le1s1EJvZqdoo6aiUEEtcRTZgJhmh5s/QXtKFgGvH6hs3JL0AW3J/zTt5y6KukWFyqQsJMYxf5STWYJ/rllJHnD+68G7Ki5c7CysS+eKYIqwk/r7R0bxnkM4faOVLbe0qUHJ/SvUOkRvwI2otQwN26K+mk7t9vs/t8P+8dmZyFXQBu6ffWgOxDb3Pwv7HBcUyg+5NnJeVawJULIYPWmKiX17Xfgz4uuC6pKPGabADYcfmjKhLei6BuljZQBwV33yS7CzMW8AQopbkg1ygOtES26fTjR9no3vCSaVd7ZMoUFs4Rk5W2EX5HvTWUtt8JOp9RevgK4axP698z6e2ywx2vtG5X18inNbOv9EqEmmkYByOeYxogj3owCE9KPBLf77+fCG8WaDyM/mPoQSnYb8z8JGYa95kk0w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jun 29, 2026 at 02:20:28PM +0200, David Hildenbrand (Arm) wrote: > On 6/27/26 09:21, Qi Zheng wrote: > > From: Qi Zheng > > > > Therefore, we are wondering if we can introduce "reserved THP", which is THP > > that can be reserved. It can be consumed through methods like madvise(), while > > normal memory allocation cannot consume it. > > madvise(). Gah. No :) > Without going into the nitty-gritty of the set here - Reserved : I care about whether this succeeeds. - Transparent: I don't care. These things are mutually exclusive, so "Reserved THP" is confusing. Maybe this makes more sense as mmap() MAP_ flags: - pre-allocates at the desired size - fails entirely if it fails Since the intent is to *reserve* it anyway, it makes sense that this would be a pre-populate directive regardless, so no lazy-faulting. Then userland can ask for what it wants and if the kernel can't produce it - allocation failed. The underlying system can otherwise use whatever tricks it wants (cma, reserved pages, etc) to get there from here, and all the swap semantics otherwise live in normal interactions (mlock, madvise, etc). Rik's work [0] is trying to move the allocator toward more reliable hugepage allocation with the intent of making THPs more reliable in general. Maybe these things meet in the middle. ~Gregory [0] https://lore.kernel.org/all/20260520150018.2491267-1-riel@surriel.com/