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 1268DCA9ECF for ; Mon, 4 Nov 2019 08:13:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E04EC21744 for ; Mon, 4 Nov 2019 08:13:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727758AbfKDINU (ORCPT ); Mon, 4 Nov 2019 03:13:20 -0500 Received: from mx2.suse.de ([195.135.220.15]:42010 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726100AbfKDINU (ORCPT ); Mon, 4 Nov 2019 03:13:20 -0500 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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