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Thu, 29 Oct 2026 00:12:16 -0700 (PDT) Received: from localhost.localdomain ([101.44.96.6]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae6f01e8a5sm1180018a91.0.2026.10.29.00.12.11 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 29 Oct 2026 00:12:16 -0700 (PDT) Sender: Yilei Zheng From: Yilei Zheng To: Muchun Song Cc: Muchun Song , Andrew Morton , Dan Williams , David Hildenbrand , Oscar Salvador , Pankaj Gupta , linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-cxl@vger.kernel.org, Vishal Verma , Dave Jiang , Alison Schofield , Mike Rapoport , Ira Weiny , Jan Kara , Matthew Wilcox , Lorenzo Stoakes , Vlastimil Babka , Michal Hocko , Qi Zheng Subject: Re: [PATCH 3/4] mm: add shared read-only vmemmap support for FS-DAX Date: Thu, 29 Oct 2026 15:12:06 +0800 Message-Id: <20261029071206.19059-1-trilith.zheng@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <2E5C10CF-F3E0-4694-965C-B0E432A1A962@linux.dev> References: <20260903122128.12264-1-songmuchun@bytedance.com> <20260903122128.12264-4-songmuchun@bytedance.com> <20261027065723.66564-1-trilith.zheng@gmail.com> <4c9741cf-ac62-41d4-9c7a-7d5ceea4a8e1@linux.dev> <20261029030511.12004-1-trilith.zheng@gmail.com> <2E5C10CF-F3E0-4694-965C-B0E432A1A962@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit I forgot to mention the tool execution case in my last mail. Those microVMs start, run a small task, and exit. DAX is there to save memory, but the vmemmap is allocated for the whole image. A 2 GiB image pays 32 MiB of vmemmap even if a microVM only reads a few MB, so for those microVMs the DAX setup can use more memory than the same image on virtio-blk. That is also a case this series fixes for us.