From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751815AbeA3LmY (ORCPT ); Tue, 30 Jan 2018 06:42:24 -0500 Received: from mail.netline.ch ([148.251.143.178]:44292 "EHLO netline-mail3.netline.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751718AbeA3LmX (ORCPT ); Tue, 30 Jan 2018 06:42:23 -0500 Subject: Re: [RFC] Per file OOM badness To: =?UTF-8?Q?Nicolai_H=c3=a4hnle?= , christian.koenig@amd.com, Michal Hocko , Roman Gushchin Cc: linux-mm@kvack.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org References: <20180118170006.GG6584@dhcp22.suse.cz> <20180123152659.GA21817@castle.DHCP.thefacebook.com> <20180123153631.GR1526@dhcp22.suse.cz> <20180124092847.GI1526@dhcp22.suse.cz> <583f328e-ff46-c6a4-8548-064259995766@daenzer.net> <20180124110141.GA28465@dhcp22.suse.cz> <36b49523-792d-45f9-8617-32b6d9d77418@daenzer.net> <20180124115059.GC28465@dhcp22.suse.cz> <381a868c-78fd-d0d1-029e-a2cf4ab06d37@gmail.com> <20180130093145.GE25930@phenom.ffwll.local> <3db43c1a-59b8-af86-2b87-c783c629f512@daenzer.net> <3026d8c5-9313-cb8b-91ef-09c02baf27db@amd.com> <445628d3-677c-a9f8-171f-7d74a603c61d@daenzer.net> <82d5894f-f4ea-98cc-068a-5d470f5267df@gmail.com> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Message-ID: Date: Tue, 30 Jan 2018 12:42:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <82d5894f-f4ea-98cc-068a-5d470f5267df@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-01-30 12:36 PM, Nicolai Hähnle wrote: > On 30.01.2018 12:34, Michel Dänzer wrote: >> On 2018-01-30 12:28 PM, Christian König wrote: >>> Am 30.01.2018 um 12:02 schrieb Michel Dänzer: >>>> On 2018-01-30 11:40 AM, Christian König wrote: >>>>> Am 30.01.2018 um 10:43 schrieb Michel Dänzer: >>>>>> [SNIP] >>>>>>> Would it be ok to hang onto potentially arbitrary mmget references >>>>>>> essentially forever? If that's ok I think we can do your process >>>>>>> based >>>>>>> account (minus a few minor inaccuracies for shared stuff perhaps, >>>>>>> but no >>>>>>> one cares about that). >>>>>> Honestly, I think you and Christian are overthinking this. Let's try >>>>>> charging the memory to every process which shares a buffer, and go >>>>>> from >>>>>> there. >>>>> My problem is that this needs to be bullet prove. >>>>> >>>>> For example imagine an application which allocates a lot of BOs, then >>>>> calls fork() and let the parent process die. The file descriptor lives >>>>> on in the child process, but the memory is not accounted against the >>>>> child. >>>> What exactly are you referring to by "the file descriptor" here? >>> >>> The file descriptor used to identify the connection to the driver. In >>> other words our drm_file structure in the kernel. >>> >>>> What happens to BO handles in general in this case? If both parent and >>>> child process keep the same handle for the same BO, one of them >>>> destroying the handle will result in the other one not being able to >>>> use >>>> it anymore either, won't it? >>> Correct. >>> >>> That usage is actually not useful at all, but we already had >>> applications which did exactly that by accident. >>> >>> Not to mention that somebody could do it on purpose. >> >> Can we just prevent child processes from using their parent's DRM file >> descriptors altogether? Allowing it seems like a bad idea all around. > > Existing protocols pass DRM fds between processes though, don't they? > > Not child processes perhaps, but special-casing that seems like awful > design. Fair enough. Can we disallow passing DRM file descriptors which have any buffers allocated? :) -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer