From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D130DC282CC for ; Wed, 6 Feb 2019 20:20:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8CEF020823 for ; Wed, 6 Feb 2019 20:20:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Ab/ZKKur" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8CEF020823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1B15D8E00F8; Wed, 6 Feb 2019 15:20:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 13A3E8E00F3; Wed, 6 Feb 2019 15:20:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EF5A38E00F8; Wed, 6 Feb 2019 15:20:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) by kanga.kvack.org (Postfix) with ESMTP id AAF138E00F3 for ; Wed, 6 Feb 2019 15:20:26 -0500 (EST) Received: by mail-pl1-f198.google.com with SMTP id t10so5688743plo.13 for ; Wed, 06 Feb 2019 12:20:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:date:from:to:cc:subject :message-id:references:mime-version:content-disposition:in-reply-to :user-agent; bh=zxiuA+kMki/UhwSsnRN7805PLjtsIi6PGZFOiQ1YwQk=; b=NNmrOzt5Fa0BDjylHTSdNyLlAeUNClXajB+uL0ie9le+IcKiDtCemaSEwieQIusghH HXvcFUUFdKmW+dxIHcNldw5fTEMIfqFncdMVQWOh1zp5a2xaD2Bbb2dAONPNc9HOtWD9 R4+KM2Zrr+48Q0sC5yUFZ0Jy3r6AcOHXBX54MwbO24OzUSfu4n7lrj6p4lnb0slllGJa MjGVqJCn1uwm+D4fVgSr0nfBZhtqb8NdD3iUafRF34Ptir1hGCMDO13nbptb4p3k7dsD lfGcGAmH4Vbu5gnzHxfdLFa4WqpRpXz84Qyqasz+7aOv/I6wGyEDfew+IknYy0y6+b0+ Ij7w== X-Gm-Message-State: AHQUAuZ2bUCN+sp90glXH8fDcx5Aobmflk8MP016V90X2F97WUUSUrDe NFbUHiIJ+ghNj9J70PfVGsBiMcaCjsyILU1ZY10GcNh7yYgxcHo5o0s9gSSM7Hm+wTKSNwA/Lzz X0MdBbBOBsL15ABEkQKawMGqxNOp+cIWgOyApyL2sFf7WWvWVqr/uI1HZIAGtrePRag== X-Received: by 2002:a17:902:3124:: with SMTP id w33mr12556788plb.241.1549484426356; Wed, 06 Feb 2019 12:20:26 -0800 (PST) X-Google-Smtp-Source: AHgI3Ib0SqxYeSouar8XjUs1ioCXGchhPLm+OAWZu50KD5M24EtGWy1bxchOXlmI5QUeiZnOSlZw X-Received: by 2002:a17:902:3124:: with SMTP id w33mr12556742plb.241.1549484425692; Wed, 06 Feb 2019 12:20:25 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1549484425; cv=none; d=google.com; s=arc-20160816; b=IlNn0DkxLJFyLvuE+V5YTMzYef8mN6IRN+NAdQNyPObTtX65lQRiHBFEGiyKvv5C8T YklZljLBDNKJ+qpK0gntD1QM+l36mfWMs967nU9lqJQl3XZgvPWzKGYLG0kj/+JeXW5L 4durPLxp1lbCsgdZd+pkGFgNc6KXQ6ync/llzwoxMDICeIAdjQ0i1zS2spHe+M3FocT6 /BFJdf/4NQ4LU0GqSv+YS022y5iN6G93sI/zYgMFaKbeT/PF11Sp9qa3BV8wl1AEkusF NHVH7eNOwoMIc8ChYFgaR3XnSOnWJL/KhwYptN4OPmOAONCAGOWahvJ2Xc9onjUA92yt lLyA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature; bh=zxiuA+kMki/UhwSsnRN7805PLjtsIi6PGZFOiQ1YwQk=; b=oI9ANkS5gWVQf+XPjc4+WQovOF4N13pRkw9+InAW93ku22zUkFYgoQXqxTyqObqBz4 fbKmFutgX6kYjsOTZTGmEjGpT9u7kgkbVag0IRLzPjaGn1oZKVh0rjxraXLSyVGj/a7I Le9kF9RWYOTl8/AbwQiGfyfJHjzCYVGhE1TV1HL7Hofau7AdPOMdZoFUrgt1g9k+QD0Y xljxhmq4x/XCXLENf5I4K0QHVjw0b7S04yeK5RMteYUzYgWfmixJXKFjgmc5beS8CAd9 +qgtfsv12k2UJ/Ep7Jg7mvFmX/zK9hvHINtRPL/4NGJKAs6okWSvvnpDqBlaQJDs/KHf cQfQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b="Ab/ZKKur"; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id l66si6942370pfi.5.2019.02.06.12.20.25 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 06 Feb 2019 12:20:25 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@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="Ab/ZKKur"; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@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=zxiuA+kMki/UhwSsnRN7805PLjtsIi6PGZFOiQ1YwQk=; b=Ab/ZKKurlrlfBf27eXyZXOAoc vMRey/USNDaTEnIgHG3mGDD3ZLLM1aisiG7e0shzKeua0xOugZ2EixdhKk8B/pBQs/aw+NSJl72+5 WMkK95M7MEOG8rcRdlRibITDjzsg7gYTfhH7d/kL6LnJUluCZ+vN+M8uKloKFKAm911wua3K4IyY3 53oawd2oTBqnpQUtZm7AniaJvkc/6VKZ2z8miEukueTSg6krxGKQwIAjLR9/OjAHNFuYR9jAAjSIv YJJS0o8Mt+ikxTAoYusqDbJtLVPBy3+FsI3TMamjD6SZsPHbOoiOqU0ENz7ItusFaSmT4pmdeN7qx ME+59Vxyw==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1grTgD-0003Sc-As; Wed, 06 Feb 2019 20:20:21 +0000 Date: Wed, 6 Feb 2019 12:20:21 -0800 From: Matthew Wilcox To: Doug Ledford Cc: 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: <20190206202021.GQ21860@bombadil.infradead.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) 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, 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. It's straightforward to migrate text pages from one DIMM to another; you remove the PTEs from the CPU's page tables, copy the data over and pagefaults put the new PTEs in place. We don't have a way to do similar things to an RDMA device, do we?