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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 7945CC433E0 for ; Wed, 22 Jul 2020 14:30:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 343402065F for ; Wed, 22 Jul 2020 14:30:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=shipmail.org header.i=@shipmail.org header.b="J9tPxlDO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732513AbgGVOaR (ORCPT ); Wed, 22 Jul 2020 10:30:17 -0400 Received: from pio-pvt-msa2.bahnhof.se ([79.136.2.41]:34246 "EHLO pio-pvt-msa2.bahnhof.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729126AbgGVOaR (ORCPT ); Wed, 22 Jul 2020 10:30:17 -0400 Received: from localhost (localhost [127.0.0.1]) by pio-pvt-msa2.bahnhof.se (Postfix) with ESMTP id 48E123F4A0; Wed, 22 Jul 2020 16:30:13 +0200 (CEST) Authentication-Results: pio-pvt-msa2.bahnhof.se; dkim=pass (1024-bit key; unprotected) header.d=shipmail.org header.i=@shipmail.org header.b=J9tPxlDO; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at bahnhof.se Received: from pio-pvt-msa2.bahnhof.se ([127.0.0.1]) by localhost (pio-pvt-msa2.bahnhof.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id qxFCURGVkHmS; Wed, 22 Jul 2020 16:30:12 +0200 (CEST) Received: from mail1.shipmail.org (h-205-35.A357.priv.bahnhof.se [155.4.205.35]) (Authenticated sender: mb878879) by pio-pvt-msa2.bahnhof.se (Postfix) with ESMTPA id 1A2CA3F418; Wed, 22 Jul 2020 16:30:08 +0200 (CEST) Received: from [192.168.0.100] (h-205-35.A357.priv.bahnhof.se [155.4.205.35]) by mail1.shipmail.org (Postfix) with ESMTPSA id 9A868362551; Wed, 22 Jul 2020 16:30:09 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=shipmail.org; s=mail; t=1595428209; bh=aSl2HPnj0FsbxHaER8NWcOJP1lNOrY9LWA/Axz0+ARc=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=J9tPxlDOyXydSD3slE2p0eNPxX3EnMvw3rCZ+KeUxQDcoGObCCmP0ZpThy3LkSLvn JFDx/0w+cDSwmSJPVlusn15yK+G3RxeKW7CfFJ53qq7wa1RdTrTaRIDyHU/i04o+R3 QCfhbTQJ1VJwrsAlbklRs6g9PT7fFz7pDrquF7hI= Subject: Re: [Linaro-mm-sig] [PATCH 1/2] dma-buf.rst: Document why indefinite fences are a bad idea To: christian.koenig@amd.com, Daniel Vetter Cc: Felix Kuehling , Daniel Stone , linux-rdma , Intel Graphics Development , Maarten Lankhorst , DRI Development , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Steve Pronovost , amd-gfx mailing list , Jason Ekstrand , Jesse Natalie , Daniel Vetter , Thomas Hellstrom , Linux Media Mailing List , Dave Airlie , Mika Kuoppala References: <20200707201229.472834-4-daniel.vetter@ffwll.ch> <93b673b7-bb48-96eb-dc2c-bd4f9304000e@shipmail.org> <20200721074157.GB3278063@phenom.ffwll.local> <3603bb71-318b-eb53-0532-9daab62dce86@amd.com> <57a5eb9d-b74f-8ce4-7199-94e911d9b68b@shipmail.org> <805c49b7-f0b3-45dc-5fe3-b352f0971527@shipmail.org> <92393d26-d863-aac6-6d27-53cad6854e13@shipmail.org> <8fd999f2-cbf6-813c-6ad4-131948fb5cc5@shipmail.org> <697d1b5e-5d1c-1655-23f8-7a3f652606f3@shipmail.org> From: =?UTF-8?Q?Thomas_Hellstr=c3=b6m_=28Intel=29?= Message-ID: Date: Wed, 22 Jul 2020 16:30:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 2020-07-22 16:23, Christian König wrote: > Am 22.07.20 um 16:07 schrieb Daniel Vetter: >> On Wed, Jul 22, 2020 at 3:12 PM Thomas Hellström (Intel) >> wrote: >>> On 2020-07-22 14:41, Daniel Vetter wrote: >>>> I'm pretty sure there's more bugs, I just haven't heard from them yet. >>>> Also due to the opt-in nature of dma-fence we can limit the scope of >>>> what we fix fairly naturally, just don't put them where no one cares >>>> :-) Of course that also hides general locking issues in dma_fence >>>> signalling code, but well *shrug*. >>> Hmm, yes. Another potential big problem would be drivers that want to >>> use gpu page faults in the dma-fence critical sections with the >>> batch-based programming model. >> Yeah that's a massive can of worms. But luckily there's no such driver >> merged in upstream, so hopefully we can think about all the >> constraints and how to best annotate&enforce this before we land any >> code and have big regrets. > > Do you want a bad news? I once made a prototype for that when Vega10 > came out. > > But we abandoned this approach for the the batch based approach > because of the horrible performance. In context of the previous discussion I'd consider the fact that it's not performant in the batch-based model good news :) Thomas > > KFD is going to see that, but this is only with user queues and no > dma_fence involved whatsoever. > > Christian. > >> -Daniel >> >> >> >> -- >> Daniel Vetter >> Software Engineer, Intel Corporation >> http://blog.ffwll.ch >> _______________________________________________ >> amd-gfx mailing list >> amd-gfx@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/amd-gfx