From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.216.44 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793243122; b=gh/ti0hNZiV2qjK9FhhtOL55jiA3obcHtaZQgjZP4dr8KHf//rqgbw8VsZKJIS6thuYH c5FjEHjHWru2NthPGv9gELar7Um7CLhTYcLF1SfHqXFKIzdTIIkTGXUZLmnnwH6So5n8f eXwHRhsL7gLlU4sief7u1R2cps2fk1nebBH25iR+/LV/wq6273zsfL/CVhv3KPGyMYWh0 DH3Bnp9txatJR70KdueaNdpqeCzddZcn5hGyCTZpB4BrIBNgYHaN/h9Zx6ruCcskIZxmA x3lpYsyopMich1/vdfKL965qGQsoWXuDl75WaEGzDQdKmiOGWWv27BmG0C5y3XNrvzg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793243122; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Sender:From:To:Cc:Subject:Date:Message-Id:X-Mailer:In-Reply-To: References:MIME-Version:Content-Transfer-Encoding; bh=Qt+rBjELLMxb0qTKo9uNTiwBY/+V4YZH/Ya3Tn3lncw=; b=rvpk5X19Koe22/ngTtVbDhmZX8dOxi3SuTBtSo4wzwPFLBfWxKqLdvKvA8xezwRDfY8C 6vEzA4g+sHPQYfDeXhoCwFeC7b1EDUpKdOVSOhHmXOmhSwNoZW8DjXE+Ehj10VTjtsALf 5YNh8xxZc991ZEVjiN1F/Zn27E5bFLjVG8IACM1MRu+R5T+mTe2NBbt/VQm5PsTk8JzHC bAtEphVu/adftcEhanGKjKiR8XgqzWvgVcTMRsLV/KN6zFPRTBvKye73jgTg3Hn46XWeX lhVrm6UwDxVC0yRWBI+GmOiOosaoIQMvtiD5Onl2OPin0o9Q+AS9NXNAn65tv2KaahQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b="xHNh2s/Z"; arc=none smtp.remote-ip=209.85.216.44 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8F9CB606A31D for ; Thu, 29 Oct 2026 03:05:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 8F9CB606A31D Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=xHNh2s/Z Received: by mail-pj1-f44.google.com with SMTP id 98e67ed59e1d1-3ad2b3b1c02so891717a91.1 for ; Wed, 28 Oct 2026 20:05:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1793243122; x=1793847922; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:from:to:cc:subject:date :message-id:reply-to:content-type; bh=Qt+rBjELLMxb0qTKo9uNTiwBY/+V4YZH/Ya3Tn3lncw=; b=xHNh2s/ZBjEIdJDX4r+dFuo8rNJ9MVQVAR+r5+cnenMwbZpMBs1xnjBlakkyac9yTO 8bMDjuugxd7EriUc3d3oVvtIWW2p3YbNJ6KsEsKfm1ubZUETX0TsFQzRwNVFq/3LHMUv XupBgGrNQPXrLmyVezeYmQp08Rnt+GIf42xgjCkAl2khgayG0W1ZslJ/HRhejgKgtgHn aFTEyIabEusutC3KAy6fFI5jwEfnN1Cwnh8aBLn4XOw3TnjNw0MbYfUpudFWA9sLlVpm eYZpu6l7g4dB6hYU0VRew9uzv8fblmkebY0fmLw8l+APd394gUkEs5tyKa6ZltcieY09 Ysow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793243122; x=1793847922; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=Qt+rBjELLMxb0qTKo9uNTiwBY/+V4YZH/Ya3Tn3lncw=; b=T9K0viUF5o0fS66IBJIgQZQ0tomrIUdCEOOgVx/3ldKOwDoDAfNZTfhwbSBL6cXQ8b 5rZK8eoo/1Qfvl9ZmuEwFqS7VXF3eTG0np/l/GilzZaafiWW5iSF21gzuAbvmwGIiP1H HP5HqTR322jPyCYBmNKGESsduaJceggOPm/dJ3BBPvj6d5ZqPoeltroUfXRL4INiKJJ4 D5jLnxf2mBmw88SXaC97DKJecX8WRrF4jTQ7TwIeaVC3sUsnrN2ijnzDxtnKLpllsPSy 87A0R06TzAxbF0mUdirvPQsPPTrjdR+iWI14mMp6sJJBXWx3ZupvFbQC7xk/3gSCV/Uw yghw== X-Forwarded-Encrypted: i=1; AKwUvBzbSrEa5gGB99cw4jKI3vXWXeMZNzqp1VCWt/gKGaXQ54GkdC8/mO3ZZt7Z3PAICP4nOLP9F6LcpmNrXvc=@vger.kernel.org X-Gm-Message-State: AFq9FYIL5tmWZR9NoiVbWns+y8y9twHeBZXt5M+z+cqHwf6VQJyyhzrJ l2kZIp93Vd/s5YT62I3GzmNhie2ymM5lMpp9YpC/edqdmWIsol67LQm7 X-Gm-Gg: AYBFou3b6I7rQhOP3MZeTWbBAzw7ywRT8vZXGWmIHky9zaEvTfxBCNDfk7FmqI/JNnd KDcknalYTmdIQQs6R0Ke/ROs/ZVAkcDSlvW2ss4azQGl/M2PuQeJAgixio4rVTmsf8iR9RsMA8g KTmjjtL+UAoTjg9RTOlmQKyYz5oEwJqoUuDLWIRZXgAjqU0sBKGXPbf3/zlcRH5NjoKcWHaFsP7 nVVBMp/LPL71rkqPTB07YvSGjx811JoW5DWvdV8Qyq6DGFZnHTSCaoIEcPmZGVL2ZUlJwn8iMi/ F7yVNW9TAhK7p3bj9PH+lf7C/3tz26saTS+RGNT7ucPhADtD3JpIybBQTX9W9RIWcdBRSI+qZwh qib9213rYy4hEggf3GnR4hYKdKUQCPYhSRg2Zk1F7NB0pcGyNI4AxVJljEyiHKbLgLtKG0XZ3SC Vhyw0p5jDnwrkmodux++gQML0j4VC8FKpxofo8q6uHK2FRldxPojcRSepHB1olXXqlH2k9jXmIx yYFgZ6u+yqocAwg1UEqFtsSV1ZqfCP0Uea9MCQFIkVD3rDwKfWOCZ5xQjr7VigmJjwL6DkEOaEC 5MUPYi616KS1IU3E7rzrm3vZL/pjcjBgqdgYSYwDfSV1n484iVHi8w== X-Received: by 2002:a17:90b:3810:b0:3ac:b08a:ed2c with SMTP id 98e67ed59e1d1-3ae5822fb8amr3357641a91.40.1793243121828; Wed, 28 Oct 2026 20:05:21 -0700 (PDT) Received: from localhost.localdomain ([101.44.96.6]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae6e9583c1sm1932931a91.10.2026.10.28.20.05.16 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 28 Oct 2026 20:05:21 -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 11:05:11 +0800 Message-Id: <20261029030511.12004-1-trilith.zheng@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <4c9741cf-ac62-41d4-9c7a-7d5ceea4a8e1@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> 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 Hi Muchun, > Thank you very much for the test, so in your scenario, this is also > the behavior of your real workload (mainly read/write-based, rather > than mmap), right? Yes. We mount read-only rootfs images over virtio-pmem and FS-DAX. Most file access goes through normal read/write. mmap is only used for loading binaries and shared libraries at startup, which is a small part of the image. > To be fair, it does fix the issue, but it's not very clean. I might > do some code cleanup first to solve this more gracefully. I want to > move the initialization to where the template page is allocated, > similar to what section-based vmemmap optimization does. Makes sense. Initializing it at allocation time is cleaner. > Thanks for the analysis and suggestions. However, the reason I > haven't sent out v2 yet is that I've been trying to refactor the > vmemmap optimization logic to make FS_DAX support cleaner. I think > I'll probably do some code refactoring first. Understood. It would also help if the refactor could support subsection (2 MiB) alignment, so any 2 MiB-aligned device can use the optimization without padding to a 128 MiB multiple. > I'cc you next time if you'd like to help me test. Sounds good. Please Cc me when you post v2 and I'll be glad to test. Best regards, Yilei