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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 33B3FCCA479 for ; Mon, 18 Jul 2022 16:01:10 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id DBB7F12A8A8; Mon, 18 Jul 2022 16:01:02 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id C75A412A8A8; Mon, 18 Jul 2022 16:01:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1658160060; x=1689696060; h=date:from:to:cc:subject:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=C6vWqUcyXQkTAuAAqqcnVbId6I4b0LLhuzC6Emj2LTg=; b=X+pOoCTQRYvBlqq3ocuuR6hue3h0+yss3OQHfb2vGo89y1TTAUJGFspA yS/V3CPn4nP7njEM2HrJzekplS5RMquTM8+9Y9jRDkdRnwcKcvZISZ+sz djsKDRef/QEensow2/ZbhKfbVt35hvnMMJFVDKUpZJvn3oPGQyCts9+Hp KtUGh/W+Nc0ST7U9eKlvRSfS2ht+9dlx3zFbam7z0wqWoQFwMJCdnsT1i G4e/1+tq8iesFPsQL1OW9QpQd8ogVjoriRYvemNSr3NIMfXmD1RhdWK0f KUGMdQPumeiPop2I/vEtEa46Rsc/ljDxhiGZQCAznULQa/+MBKrgbVChx g==; X-IronPort-AV: E=McAfee;i="6400,9594,10412"; a="285014673" X-IronPort-AV: E=Sophos;i="5.92,281,1650956400"; d="scan'208";a="285014673" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2022 09:00:59 -0700 X-IronPort-AV: E=Sophos;i="5.92,281,1650956400"; d="scan'208";a="655344616" Received: from maurocar-mobl2.ger.corp.intel.com (HELO maurocar-mobl2) ([10.249.35.85]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2022 09:00:56 -0700 Date: Mon, 18 Jul 2022 18:00:54 +0200 From: Mauro Carvalho Chehab To: Tvrtko Ursulin Subject: Re: [Intel-gfx] [PATCH v2 04/21] drm/i915/gt: Only invalidate TLBs exposed to user manipulation Message-ID: <20220718180054.048929ef@maurocar-mobl2> In-Reply-To: <72a40626-ee71-fffe-3816-933fbec92c4d@linux.intel.com> References: <72a40626-ee71-fffe-3816-933fbec92c4d@linux.intel.com> X-Mailer: Claws Mail 4.1.0 (GTK 3.24.34; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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: , Cc: Thomas =?UTF-8?B?SGVsbHN0?= =?UTF-8?B?csO2bQ==?= , David Airlie , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Chris Wilson , Rodrigo Vivi , Dave Airlie , stable@vger.kernel.org, Mauro Carvalho Chehab Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, 18 Jul 2022 14:39:17 +0100 Tvrtko Ursulin wrote: > On 14/07/2022 13:06, Mauro Carvalho Chehab wrote: > > From: Chris Wilson > > > > Don't flush TLBs when the buffer is only used in the GGTT under full > > control of the kernel, as there's no risk of concurrent access > > and stale access from prefetch. > > > > We only need to invalidate the TLB if they are accessible by the user. > > That helps to reduce the performance regression introduced by TLB > > invalidate logic. > > > > Cc: stable@vger.kernel.org > > Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store") > > Do we really need or want stable and fixes on this one? > > What do we think the performance improvement is, given there's very > little in GGTT, which is not mapped via PPGTT as well? > > I think it is safe, but part of me would ideally not even want to think > about whether it is safe, if the performance improvement is > non-existent. Which I can't imagine how there would be? Makes sense. Patch 6 actually ends removing the code doing that, so I'll just fold this patch with patch 6, in order to avoid adding something that will later be removed. Regards, Mauro