From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m92250.xmail.ntesmail.com (mail-m92250.xmail.ntesmail.com [103.126.92.250]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 21FA11426F; Wed, 24 Apr 2024 07:12:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=103.126.92.250 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713942772; cv=none; b=cOfG5r+/UK1C0kSDVg+p9V7aqVjSUiGGLmCy0DC2HBNOfdP85C+gsdP/StaBX/wQzs++Pwm4pM4kfQdEcLu5S+8LP6/pXzeJxSsO/Ev6UYFY4gSQu145wOzaenyHGyXdPtWFQkCEv0hY1+Iur8HFdqbjsXK0ZqFtebZP9RvyQQ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713942772; c=relaxed/simple; bh=1qq2VCoGtIPzTz8r0fxP/6/Cncs/mnnfnOfT+3WWaB0=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=dUMwrRQ0BPmrE2xDypGptiPZFH2qwASeG9C2QIIkZEuHssgJBaioiWgB6+LJZgKX5fKc0ZuZsllZsYflokycRlL9VxhYbM/Xzgu8sJTNqcXPJGHJ1CmrPC9h93g1YgXtJla/hzVBHFaTeG+dYIcp0IZtagDVpTPliZllWnCQPyI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=easystack.cn; spf=pass smtp.mailfrom=easystack.cn; arc=none smtp.client-ip=103.126.92.250 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=easystack.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=easystack.cn Received: from [192.168.122.189] (unknown [218.94.118.90]) by smtp.qiye.163.com (Hmail) with ESMTPA id 0DA0E86023D; Wed, 24 Apr 2024 14:33:30 +0800 (CST) Subject: Re: [PATCH RFC 0/7] block: Introduce CBD (CXL Block Device) To: Dan Williams , axboe@kernel.dk, John Groves Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, Dongsheng Yang References: <20240422071606.52637-1-dongsheng.yang@easystack.cn> <66288ac38b770_a96f294c6@dwillia2-mobl3.amr.corp.intel.com.notmuch> From: Dongsheng Yang Message-ID: Date: Wed, 24 Apr 2024 14:33:28 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <66288ac38b770_a96f294c6@dwillia2-mobl3.amr.corp.intel.com.notmuch> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFJQjdXWS1ZQUlXWQ8JGhUIEh9ZQVlCSx0aVk0aTU1KGkkeGEkfTlUZERMWGhIXJBQOD1 lXWRgSC1lBWUlKQ1VCT1VKSkNVQktZV1kWGg8SFR0UWUFZT0tIVUpNT0lMTlVKS0tVSkJLS1kG X-HM-Tid: 0a8f0ecf2fe2023ckunm0da0e86023d X-HM-MType: 1 X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6NRA6MDo*Sjc1DREPQhVRARgZ NTNPCj5VSlVKTEpIQk9LT0pLTENMVTMWGhIXVR8UFRwIEx4VHFUCGhUcOx4aCAIIDxoYEFUYFUVZ V1kSC1lBWUlKQ1VCT1VKSkNVQktZV1kIAVlBSE5IQzcG 在 2024/4/24 星期三 下午 12:29, Dan Williams 写道: > Dongsheng Yang wrote: >> From: Dongsheng Yang >> >> Hi all, >> This patchset introduce cbd (CXL block device). It's based on linux 6.8, and available at: >> https://github.com/DataTravelGuide/linux >> > [..] >> (4) dax is not supported yet: >> same with famfs, dax device is not supported here, because dax device does not support >> dev_dax_iomap so far. Once dev_dax_iomap is supported, CBD can easily support DAX mode. > > I am glad that famfs is mentioned here, it demonstrates you know about > it. However, unfortunately this cover letter does not offer any analysis > of *why* the Linux project should consider this additional approach to > the inter-host shared-memory enabling problem. > > To be clear I am neutral at best on some of the initiatives around CXL > memory sharing vs pooling, but famfs at least jettisons block-devices > and gets closer to a purpose-built memory semantic. > > So my primary question is why would Linux need both famfs and cbd? I am > sure famfs would love feedback and help vs developing competing efforts. Hi, Thanks for your reply, IIUC about FAMfs, the data in famfs is stored in shared memory, and related nodes can share the data inside this file system; whereas cbd does not store data in shared memory, it uses shared memory as a channel for data transmission, and the actual data is stored in the backend block device of remote nodes. In cbd, shared memory works more like network to connect different hosts. That is to say, in my view, FAMfs and cbd do not conflict at all; they meet different scenario requirements. cbd simply uses shared memory to transmit data, shared memory plays the role of a data transmission channel, while in FAMfs, shared memory serves as a data store role. Please correct me if I am wrong. Thanx > . >