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[46.138.191.2]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6a59dd550bcsm13565742a12.0.2026.08.25.02.08.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Aug 2026 02:08:42 -0700 (PDT) From: Artem Lytkin To: David Hildenbrand , Matthew Wilcox Cc: Ackerley Tng , Zi Yan , Kiryl Shutsemau , Hugh Dickins , Baolin Wang , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH 0/4] Extend xas_split* to support splitting arbitrarily large entries Date: Tue, 25 Aug 2026 12:08:27 +0300 Message-ID: <20260825090827.64550-1-iprintercanon@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: <20251117224701.1279139-1-ackerleytng@google.com> <20260824194755.216000-1-iprintercanon@gmail.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, Aug 25, 2026 at 10:31:34AM +0200, David Hildenbrand (Arm) wrote: > > IOW is this driven by a real need, or just some completionist thing? > > I heard some use cases using 512M THPs on arm64 to back VMs, but it's mostly > anon pages, and not really ordinary pagecache. No real need on my side. I took the pagemap.h comment and the selftest skips as an invitation, and the one 64K user I can find on the list (Meta, in Kiryl's collapse RFC) says mTHP is what they want. Dropping the arm64 angle. > But a buddy-like split is clearly preferable. (or avoiding splitting in the > first place :) ) That path exists as xas_try_split(). What's left is the uniform split to order 0 that __folio_split() still does through xas_split_alloc(), and the only one asking for it past order 11 is guest_memfd. That's Ackerley's call; if he wants the rebase I'll do the mechanical part. Artem