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=-6.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,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 5C88DC433EF for ; Mon, 13 Sep 2021 10:52:31 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1EEBF60F12 for ; Mon, 13 Sep 2021 10:52:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1EEBF60F12 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D54D96E154; Mon, 13 Sep 2021 10:52:28 +0000 (UTC) Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7EF126E0A6; Mon, 13 Sep 2021 10:52:27 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10105"; a="208740768" X-IronPort-AV: E=Sophos;i="5.85,288,1624345200"; d="scan'208";a="208740768" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Sep 2021 03:52:26 -0700 X-IronPort-AV: E=Sophos;i="5.85,288,1624345200"; d="scan'208";a="469159921" Received: from dennis-mobl.ger.corp.intel.com (HELO [10.213.217.72]) ([10.213.217.72]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Sep 2021 03:52:24 -0700 Subject: Re: [Intel-gfx] [PATCH 23/27] drm/i915/guc: Implement no mid batch preemption for multi-lrc To: Matthew Brost Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, daniel.vetter@ffwll.ch, tony.ye@intel.com, zhengguo.xu@intel.com References: <20210820224446.30620-1-matthew.brost@intel.com> <20210820224446.30620-24-matthew.brost@intel.com> <20210910204935.GA24315@jons-linux-dev-box> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <722dd221-3867-2e27-ec48-323e8c36ae43@linux.intel.com> Date: Mon, 13 Sep 2021 11:52:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210910204935.GA24315@jons-linux-dev-box> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 10/09/2021 21:49, Matthew Brost wrote: > On Fri, Sep 10, 2021 at 12:25:43PM +0100, Tvrtko Ursulin wrote: >> >> On 20/08/2021 23:44, Matthew Brost wrote: >>> For some users of multi-lrc, e.g. split frame, it isn't safe to preempt >>> mid BB. To safely enable preemption at the BB boundary, a handshake >>> between to parent and child is needed. This is implemented via custom >>> emit_bb_start & emit_fini_breadcrumb functions and enabled via by >>> default if a context is configured by set parallel extension. >> >> FWIW I think it's wrong to hardcode the requirements of a particular >> hardware generation fixed media pipeline into the uapi. IMO better solution >> was when concept of parallel submission was decoupled from the no preemption >> mid batch preambles. Otherwise might as well call the extension >> I915_CONTEXT_ENGINES_EXT_MEDIA_SPLIT_FRAME_SUBMIT or something. >> > > I don't disagree but this where we landed per Daniel Vetter's feedback - > default to what our current hardware supports and extend it later to > newer hardware / requirements as needed. I think this only re-affirms my argument - no point giving the extension a generic name if it is so tightly coupled to a specific use case. But I wrote FWIW so whatever. It will be mighty awkward if compute multi-lrc will need to specify a flag to allow preemption, when turning off preemption is otherwise not something we allow unprivileged clients to do. So it will be kind of opt-out from unfriendly/dangerous default behaviour instead of explicit requesting it. Regards, Tvrtko