From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa4.hgst.iphmx.com (esa4.hgst.iphmx.com [216.71.154.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 1B25F21E25682 for ; Wed, 24 Jan 2018 19:56:17 -0800 (PST) From: Bart Van Assche Subject: Re: [LSF/MM TOPIC] Filesystem-DAX, page-pinning, and RDMA Date: Thu, 25 Jan 2018 04:01:43 +0000 Message-ID: <1516852902.3724.4.camel@wdc.com> References: In-Reply-To: Content-Language: en-US Content-ID: <421B4EAE84F4C14BB9A74F1146530B6F@namprd04.prod.outlook.com> MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: "dan.j.williams@intel.com" , "lsf-pc@lists.linux-foundation.org" Cc: "linux-nvdimm@lists.01.org" , "linux-rdma@vger.kernel.org" , "mhocko@kernel.org" , "hch@infradead.org" , "linux-mm@kvack.org" , "jgg@mellanox.com" List-ID: On Wed, 2018-01-24 at 19:56 -0800, Dan Williams wrote: > The get_user_pages_longterm() api was recently added as a stop-gap > measure to prevent applications from growing dependencies on the > ability to to pin DAX-mapped filesystem blocks for RDMA indefinitely > with no ongoing coordination with the filesystem. This 'longterm' > pinning is also problematic for the non-DAX VMA case where the core-mm > needs a time bounded way to revoke a pin and manipulate the physical > pages. While existing RDMA applications have already grown the > assumption that they can pin page-cache pages indefinitely, the fact > that we are breaking this assumption for filesystem-dax presents an > opportunity to deprecate the 'indefinite pin' mechanisms and move to a > general interface that supports pin revocation. > > While RDMA may grow an explicit Infiniband-verb for this 'memory > registration with lease' semantic, it seems that this problem is > bigger than just RDMA. At LSF/MM it would be useful to have a > discussion between fs, mm, dax, and RDMA folks about addressing this > problem at the core level. > > Particular people that would be useful to have in attendance are > Michal Hocko, Christoph Hellwig, and Jason Gunthorpe (cc'd). Is on demand paging sufficient as a solution for your use case or do you perhaps need something different? See also https://www.openfabrics.org/images/eventpresos/workshops2013/2013_Workshop_Tues_0930_liss_odp.pdf Thanks, Bart. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm