From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.168 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793259109; b=LC1WlFtqkyUIlJ3h7gyVXoZXWFZWpj+dMdr+8V4dwF1CNPBk9gvgtjwX3net8H+DU2C7 M/CIF2aIJoUjdlWUjGBVzDAQTHLDKHwU+XY9linu2+gbDsf3sQ7d/dh316Mf2CqGEH3Ga SFMIF70iXmPGQ8TFTpqJ8NZ0b0WSpj5nc1acwe/r5bNEyoQ2amthNocL995/52PX9WqF0 cxEhUg7DqcSasWS9TdqKZNtYjAHvLGciFMPLfNnw6anWvIkXvz9kCB8f4YWRZiAkGnh0W Bc/Us+TxfBNe2TO/JgMP4kE529BDQ92/dSgknvAFMmDMDIHab7wJa3AKiUe/0zwrBtw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793259109; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Content-Type:Mime-Version:Subject:From: In-Reply-To:Date:Cc:Content-Transfer-Encoding:Message-Id:References: To:X-Mailer; bh=SjP7vXEfBmu5GFwxYK7lYChg0d8nniaqmFaSK+SgEpk=; b=uCJPwpxKx4fv0S5s6X+WlNf4cNsHVOSpPC53MJd6yrpI0ETdjY8QymMVnUG6soyyuIUo X8CKeCby3KdmHEtjI/ZQaoE5Bpd67vxTw1BTTA6FPXZu/GGUkDtjbmhiUuvS7O2Shd0Rk 24JWng1rdX5ooE5fCUt3i+fCurXiOUp+abJh9I0h+YwXNXQTjCIaMnjHzLoMLM8/vPjVv SrBmIFnaeV0VTdV4uGKTpDMTIqfTTxrVo7x+iftH6cgftWzwLxbskSc2azup2E6g6CiKI SpOehytrS2UvGhVX2Z/hHfwwGKnl49P3kaMWKy4R3qPfTKpU45oekLwMV6fpUup+MDg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=Jc8DaRNR; arc=none smtp.remote-ip=95.215.58.168 Received: from mta1.migadu.com (out-168.mta1.migadu.com [95.215.58.168]) (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 8972E606A322 for ; Thu, 29 Oct 2026 07:31:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 8972E606A322 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=Jc8DaRNR X-Envelope-To: linux-cxl@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=DXEk7qFnkBiqsaHKOXTg9XIqQu7fTyhLlV1PlmWC7w4=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793259100; v=1; x=1793863900; b=Jc8DaRNRuV7sUsRRCf29I0aef6P7zPJYdi3W115kdfpYv4v5EgWorsqy5pjSISuh6odkhk3x dXEoSiVXt6tvM2W0GxvQzDOcHJp2eLioFEW60AAkr4mjGrVEvOsK1ZqZ6w/hUSn4lBb6BHufaTe iTEoujkDldKZ6aWbKnyx4UKw= X-Envelope-To: linux-cxl@vger.kernel.org Received: by mta11.migadu.com with ESMTPS id bb58316c57a2d4df; Thu, 29 Oct 2026 07:31:40 +0000 X-Mizu-Trace-ID: bb58316c57a2d4df X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.12\)) Subject: Re: [PATCH 3/4] mm: add shared read-only vmemmap support for FS-DAX From: Muchun Song In-Reply-To: <20261029071206.19059-1-trilith.zheng@gmail.com> Date: Thu, 29 Oct 2026 15:31:20 +0800 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 Content-Transfer-Encoding: 7bit Message-Id: 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> <20261029071206.19059-1-trilith.zheng@gmail.com> To: Yilei Zheng X-Mailer: Apple Mail (2.3901.100.1.1.12) > On Oct 29, 2026, at 15:12, Yilei Zheng wrote: > > 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. Thanks for sharing. I think in this scenario it also saves boot time. I'm not sure how significant that is, though, since the number of vmemmap pages isn't large enough to be noticeable. Thanks.