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 608D8C83F1B for ; Thu, 10 Jul 2025 15:50:20 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id EE50610E92F; Thu, 10 Jul 2025 15:50:19 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="jsfdm1Zm"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) by gabe.freedesktop.org (Postfix) with ESMTPS id 54EDF10E914 for ; Thu, 10 Jul 2025 15:50:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1752162618; x=1783698618; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=8qKwoMldSoFJAqR2IgLUMw+Ke+CgyWISgmL5Uhpawxg=; b=jsfdm1Zm0+FrHEQoUM7UNklLQ2KyvyX2VgM9v34H3DWygSCZ4wUFUgCt paMXdLO1em2gX/b7pF5T4jb7SWJEjsVDRQwCRZog8GOywjptgN2wgGp6f VvnGfGK9gCzUK95Pb7BfYt4ajczzN9wzPGtvKZIxT+fA7HZ1fqDCgIjT8 tiHKqtvnWweX+zyVPW6htc/k7uBNDkNYH2I4HA/IqQueLET912C/O3kjx LCs/0qCMw8i3WgQ6RkFXkQl/LbvF3o5m0afJQzTlNajOuw9tVUYdUek45 cHxgt3InpaApdUr7njAen5qzF+1kgHm2H+E68wtthOwFrvzBm+M6O0UCY w==; X-CSE-ConnectionGUID: RREi0zN6RiOfKFoKTSJgTA== X-CSE-MsgGUID: uIOotI24Q4OZyIQbyi3nBg== X-IronPort-AV: E=McAfee;i="6800,10657,11490"; a="57061969" X-IronPort-AV: E=Sophos;i="6.16,300,1744095600"; d="scan'208";a="57061969" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2025 08:50:18 -0700 X-CSE-ConnectionGUID: j3yqM9L8T0mJRY8InUSTCg== X-CSE-MsgGUID: HGzhJdOlT7e/xQQ4nEl2SA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,300,1744095600"; d="scan'208";a="161815976" Received: from klitkey1-mobl1.ger.corp.intel.com (HELO stinkbox) ([10.245.244.160]) by orviesa005.jf.intel.com with SMTP; 10 Jul 2025 08:50:15 -0700 Received: by stinkbox (sSMTP sendmail emulation); Thu, 10 Jul 2025 18:50:13 +0300 Date: Thu, 10 Jul 2025 18:50:13 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Mike Galbraith Cc: Sebastian Andrzej Siewior , Ben Hutchings , linux-rt-users@vger.kernel.org, intel-gfx@lists.freedesktop.org, Debian kernel maintainers Subject: Re: PREEMPT_RT vs i915 Message-ID: References: <7c42fe5a6158445e150e7d63991767e44fc36d3d.camel@decadent.org.uk> <20250709194443.lkevdn6m@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Thu, Jul 10, 2025 at 06:52:58AM +0200, Mike Galbraith wrote: > On Wed, 2025-07-09 at 23:09 +0300, Ville Syrjälä wrote: > > On Wed, Jul 09, 2025 at 09:44:43PM +0200, Sebastian Andrzej Siewior wrote: > > > On 2025-07-09 20:30:26 [+0300], Ville Syrjälä wrote: > > > > > > > > > > It seems like the critical uncore lock is currently held in a lot of > > > > > places and potentially for a long time. > > > > > > > > It shouldn't be held for that long. I think it should just be > > > > a raw spinlock. > > > > > > What about I resubmit the series and we look again? I don't think the > > > lock should be made raw just to be done with it. > > > > Until someone actually does the work to confirm the thing is working > > reliably there's no point in posting anything. > > What does that entail? Basic testing would be something like this: - enable CONFIG_DRM_I915_DEBUG_VBLANK_EVADE - set i915.enable_dsb=0 to make sure everything takes the mmio path - stress the heck out of it and make sure the histogram doesn't look significantly worse than on !RT (kms_atomic_transition --extended might take care of the display side here, but it should probably be accompanied with some horrendous system loads which is a less well defined part) - ideally do that on a potato (some VLV/CHV (Atom) thing would probably be a good candidate) - repeat with lockdep enabled to make everything even harder -- Ville Syrjälä Intel