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,USER_AGENT_SANE_2 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 8CCDFC432C3 for ; Fri, 29 Nov 2019 21:36:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 696E7206B5 for ; Fri, 29 Nov 2019 21:36:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387406AbfK2Vgf (ORCPT ); Fri, 29 Nov 2019 16:36:35 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:41720 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727304AbfK2Vge (ORCPT ); Fri, 29 Nov 2019 16:36:34 -0500 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:b93f:9fae:b276:a89a]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 1FB5F283BCB; Fri, 29 Nov 2019 21:36:33 +0000 (GMT) Date: Fri, 29 Nov 2019 22:36:29 +0100 From: Boris Brezillon To: Daniel Vetter Cc: Rob Herring , Tomeu Vizoso , Alyssa Rosenzweig , Steven Price , stable@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH 7/8] drm/panfrost: Add the panfrost_gem_mapping concept Message-ID: <20191129223629.3aaab761@collabora.com> In-Reply-To: <20191129201459.GS624164@phenom.ffwll.local> References: <20191129135908.2439529-1-boris.brezillon@collabora.com> <20191129135908.2439529-8-boris.brezillon@collabora.com> <20191129201459.GS624164@phenom.ffwll.local> Organization: Collabora X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, 29 Nov 2019 21:14:59 +0100 Daniel Vetter wrote: > On Fri, Nov 29, 2019 at 02:59:07PM +0100, Boris Brezillon wrote: > > With the introduction of per-FD address space, the same BO can be mapped > > in different address space if the BO is globally visible (GEM_FLINK) > > Also dma-buf self-imports for wayland/dri3 ... Indeed, I'll extend the commit message to mention that case. > > > and opened in different context. The current implementation does not > > take case into account, and attaches the mapping directly to the > > panfrost_gem_object. > > > > Let's create a panfrost_gem_mapping struct and allow multiple mappings > > per BO. > > > > The mappings are refcounted, which helps solve another problem where > > mappings were teared down (GEM handle closed by userspace) while GPU > > jobs accessing those BOs were still in-flight. Jobs now keep a > > reference on the mappings they use. > > uh what. > > tbh this sounds bad enough (as in how did a desktop on panfrost ever work) Well, we didn't discover this problem until recently because: 1/ We have a BO cache in mesa, and until recently, this cache could only grow (no entry eviction and no MADVISE support), meaning that BOs were staying around forever until the app was killed. 2/ Mappings were teared down at BO destruction time before commit a5efb4c9a562 ("drm/panfrost: Restructure the GEM object creation"), and jobs are retaining references to all the BO they access. 3/ The mesa driver was serializing GPU jobs, and only releasing the BO reference when the job was done (wait on the completion fence). This has recently been changed, and now BOs are returned to the cache as soon as the job has been submitted to the kernel. When that happens,those BOs are marked purgeable which means the kernel can reclaim them when it's under memory pressure. So yes, kernel 5.4 with a recent mesa version is currently subject to GPU page-fault storms when the system starts reclaiming memory. > that I think you really want a few igts to test this stuff. I'll see what I can come up with (not sure how to easily detect pagefaults from userspace).