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[195.135.220.15]) by mx.google.com with ESMTPS id cp14si10674722plb.170.2019.02.07.08.48.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 07 Feb 2019 08:48:41 -0800 (PST) Received-SPF: pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 73FC8B017; Thu, 7 Feb 2019 16:48:38 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id CFDD71E3DB5; Thu, 7 Feb 2019 17:48:36 +0100 (CET) Date: Thu, 7 Feb 2019 17:48:36 +0100 From: Jan Kara To: Doug Ledford Cc: Matthew Wilcox , Christopher Lameter , Jason Gunthorpe , Jan Kara , Ira Weiny , lsf-pc@lists.linux-foundation.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, John Hubbard , Jerome Glisse , Dan Williams , Dave Chinner , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Message-ID: <20190207164836.GL3597@quack2.suse.cz> References: <20190205175059.GB21617@iweiny-DESK2.sc.intel.com> <20190206095000.GA12006@quack2.suse.cz> <20190206173114.GB12227@ziepe.ca> <20190206175233.GN21860@bombadil.infradead.org> <47820c4d696aee41225854071ec73373a273fd4a.camel@redhat.com> <01000168c43d594c-7979fcf8-b9c1-4bda-b29a-500efe001d66-000000@email.amazonses.com> <20190206194055.GP21860@bombadil.infradead.org> <20190206202021.GQ21860@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 06-02-19 15:54:01, Doug Ledford wrote: > On Wed, 2019-02-06 at 12:20 -0800, Matthew Wilcox wrote: > > On Wed, Feb 06, 2019 at 03:16:02PM -0500, Doug Ledford wrote: > > > On Wed, 2019-02-06 at 11:40 -0800, Matthew Wilcox wrote: > > > > On Wed, Feb 06, 2019 at 07:16:21PM +0000, Christopher Lameter wrote: > > > > > though? If we only allow this use case then we may not have to worry about > > > > > long term GUP because DAX mapped files will stay in the physical location > > > > > regardless. > > > > > > > > ... except for truncate. And now that I think about it, there was a > > > > desire to support hot-unplug which also needed revoke. > > > > > > We already support hot unplug of RDMA devices. But it is extreme. How > > > does hot unplug deal with a program running from the device (something > > > that would have returned ETXTBSY)? > > > > Not hot-unplugging the RDMA device but hot-unplugging an NV-DIMM. > > Is an NV-DIMM the only thing we use DAX on? Currently yes. However KVM people are soon going to use it for their purposes as well (essentially directly sharing host page cache between guests). Honza -- Jan Kara SUSE Labs, CR