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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 8E077CA9ED3 for ; Mon, 4 Nov 2019 08:13:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5E26021D71 for ; Mon, 4 Nov 2019 08:13:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5E26021D71 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EDAF56B0007; Mon, 4 Nov 2019 03:13:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E8A786B0008; Mon, 4 Nov 2019 03:13:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D79446B000A; Mon, 4 Nov 2019 03:13:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0149.hostedemail.com [216.40.44.149]) by kanga.kvack.org (Postfix) with ESMTP id C25616B0007 for ; Mon, 4 Nov 2019 03:13:21 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 628BF181AEF1A for ; Mon, 4 Nov 2019 08:13:21 +0000 (UTC) X-FDA: 76117880202.15.error92_1d3dca948a14f X-HE-Tag: error92_1d3dca948a14f X-Filterd-Recvd-Size: 2781 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf06.hostedemail.com (Postfix) with ESMTP for ; Mon, 4 Nov 2019 08:13:20 +0000 (UTC) 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 D9D74AD8C; Mon, 4 Nov 2019 08:13:18 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id A653C1E4809; Mon, 4 Nov 2019 09:13:17 +0100 (CET) Date: Mon, 4 Nov 2019 09:13:17 +0100 From: Jan Kara To: John Hubbard Cc: Hillf Danton , linux-mm , Andrew Morton , linux-kernel , Vlastimil Babka , Jan Kara , Mel Gorman , Jerome Glisse , Dan Williams , Ira Weiny , Christoph Hellwig , Jonathan Corbet Subject: Re: [RFC] mm: gup: add helper page_try_gup_pin(page) Message-ID: <20191104081317.GB22379@quack2.suse.cz> References: <20191103112113.8256-1-hdanton@sina.com> <20191104043420.15648-1-hdanton@sina.com> <8df14660-2ce3-eda8-dc33-c4d092915656@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8df14660-2ce3-eda8-dc33-c4d092915656@nvidia.com> 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 Sun 03-11-19 22:09:03, John Hubbard wrote: > On 11/3/19 8:34 PM, Hillf Danton wrote: > > future, we have options for instance that gupers periodically release > > their references and re-pin pages after data sync the same way as the > > current flusher does. > > > > That's one idea. I don't see it as viable, given the behavior of, say, > a compute process running OpenCL jobs on a GPU that is connected via > a network or Infiniband card--the idea of "pause" really looks more like > "tear down the complicated multi-driver connection, writeback, then set it > all up again", I suspect. (And if we could easily interrupt the job, we'd > probably really be running with a page-fault-capable GPU plus and IB card > that does ODP, plus HMM, and we wouldn't need to gup-pin anyway...) > > Anyway, this is not amenable to quick fixes, because the problem is > a couple of missing design pieces. Which we're working on putting in. > But meanwhile, smaller changes such as this one are just going to move > the problems to different places, rather than solving them. So it's best > not to do that. Yeah, fully agreed here. Quick half baked fixes will make the current messy situation even worse... Honza -- Jan Kara SUSE Labs, CR