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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id g2si3714118plo.354.2019.03.13.09.03.25 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Mar 2019 09:03:25 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of batv+cb812337220b2e68da92+5680+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=HAIUAFIb; spf=pass (google.com: best guess record for domain of batv+cb812337220b2e68da92+5680+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+cb812337220b2e68da92+5680+infradead.org+hch@bombadil.srs.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=uNI5X/3NiZwWGw9ll+SGYgUYDbq0/M8f6aJJzFdlRg8=; b=HAIUAFIbqsW3BMxa/FP5NX1sG yw88chlyXN2ibo/Qu5d+gI4KxTZuL7AbNlHF0jJlGUzB21qP16G260680a2VUZLeipWU05Mn99LAu PpqWc6IqgqhyIMLkJEcfN72nGVnUjHbzkIcfuVkd6VEn+tXvqAXZavNAS5s0lksDJ73gRqY7kPQ1l JBqGDM9SN+rIsNP5uhBsIKXyqajBBvmyhH7qgWPZReT9+cYuPLpQDXyYo0hYgy6iZxpT1IxQlRJiI 3WWBkZ6SbAAmf4MBUw1zyzXRfAEkSmW5eamvKicLBu/pT0jDDL1fpCBp+a72ig51Y279e15azLyL7 29XFmWulA==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1h46Lf-0004Jg-Kg; Wed, 13 Mar 2019 16:03:19 +0000 Date: Wed, 13 Mar 2019 09:03:19 -0700 From: Christoph Hellwig To: Dave Chinner Cc: Ira Weiny , Christopher Lameter , john.hubbard@gmail.com, Andrew Morton , linux-mm@kvack.org, Al Viro , Christian Benvenuti , Christoph Hellwig , Dan Williams , Dennis Dalessandro , Doug Ledford , Jan Kara , Jason Gunthorpe , Jerome Glisse , Matthew Wilcox , Michal Hocko , Mike Rapoport , Mike Marciniszyn , Ralph Campbell , Tom Talpey , LKML , linux-fsdevel@vger.kernel.org, John Hubbard Subject: Re: [PATCH v3 0/1] mm: introduce put_user_page*(), placeholder versions Message-ID: <20190313160319.GA15134@infradead.org> References: <20190306235455.26348-1-jhubbard@nvidia.com> <010001695b4631cd-f4b8fcbf-a760-4267-afce-fb7969e3ff87-000000@email.amazonses.com> <20190310224742.GK26298@dastard> <01000169705aecf0-76f2b83d-ac18-4872-9421-b4b6efe19fc7-000000@email.amazonses.com> <20190312103932.GD1119@iweiny-DESK2.sc.intel.com> <20190312221113.GF23020@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190312221113.GF23020@dastard> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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, Mar 13, 2019 at 09:11:13AM +1100, Dave Chinner wrote: > On Tue, Mar 12, 2019 at 03:39:33AM -0700, Ira Weiny wrote: > > IMHO I don't think that the copy_file_range() is going to carry us through the > > next wave of user performance requirements. RDMA, while the first, is not the > > only technology which is looking to have direct access to files. XDP is > > another.[1] > > Sure, all I doing here was demonstrating that people have been > trying to get local direct access to file mappings to DMA directly > into them for a long time. Direct Io games like these are now > largely unnecessary because we now have much better APIs to do > zero-copy data transfer between files (which can do hardware offload > if it is available!). And that is just the file to file case. There are tons of other users of get_user_pages, including various drivers that do large amounts of I/O like video capture. For them it makes tons of sense to transfer directly to/from a mmap()ed file.