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 A8991C433EF for ; Mon, 7 Feb 2022 13:24:40 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0979F10E64A; Mon, 7 Feb 2022 13:24:40 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6A6C510E64A for ; Mon, 7 Feb 2022 13:24:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644240278; x=1675776278; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=B/4H1IW7vg5UOyJNTkzDdGn59zzNWqvz4ucYeCUFkv4=; b=UDDhghJFvxl44G+I/m+oI93d7aFAcD6WOpB2ObwlRO2wcg/g1/6xKo/3 wEub0L3ifaUI4JxH+BKu3iQSeyrGMPlRzI32EYkquLyO/gxnPYcaMvqn2 /o43bYXvv/uiTY6hX75Ofj8J7lYUlOlcWwVxtq3Ch+elOnyrQUXzea7VA qApBP6vC7m+SLZJcQbJC8OvF5fj1voP7jjkN1K2kmtXyMrYvIOgLiGHiF 0HphSjpKkJ50DmyZKUFBIEUiPbGlMdZnAouBQfMeIf7sYpMrJjmXURNwL +I8PwtLNL4KlfYeXI6oH0SgQm4nhzZz0WZpXQP1sXVYE1vz7mzDzq++2J g==; X-IronPort-AV: E=McAfee;i="6200,9189,10250"; a="335116342" X-IronPort-AV: E=Sophos;i="5.88,349,1635231600"; d="scan'208";a="335116342" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 05:24:37 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,349,1635231600"; d="scan'208";a="540095680" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.151]) by orsmga008.jf.intel.com with SMTP; 07 Feb 2022 05:24:35 -0800 Received: by stinkbox (sSMTP sendmail emulation); Mon, 07 Feb 2022 15:24:34 +0200 Date: Mon, 7 Feb 2022 15:24:34 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Tvrtko Ursulin Message-ID: References: <20220204012210.1517091-1-vivek.kasireddy@intel.com> <4475de33-22b3-edbb-2995-f72e9bcc4162@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4475de33-22b3-edbb-2995-f72e9bcc4162@linux.intel.com> X-Patchwork-Hint: comment Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915/gem: Don't try to map and fence large scanout buffers (v6) 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: , Cc: intel-gfx@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Mon, Feb 07, 2022 at 11:47:16AM +0000, Tvrtko Ursulin wrote: > > On 07/02/2022 10:58, Ville Syrjälä wrote: > > On Thu, Feb 03, 2022 at 05:22:10PM -0800, Vivek Kasireddy wrote: > >> On platforms capable of allowing 8K (7680 x 4320) modes, pinning 2 or > >> more framebuffers/scanout buffers results in only one that is mappable/ > >> fenceable. Therefore, pageflipping between these 2 FBs where only one > >> is mappable/fenceable creates latencies large enough to miss alternate > >> vblanks thereby producing less optimal framerate. > >> > >> This mainly happens because when i915_gem_object_pin_to_display_plane() > >> is called to pin one of the FB objs, the associated vma is identified > >> as misplaced and therefore i915_vma_unbind() is called which unbinds and > >> evicts it. This misplaced vma gets subseqently pinned only when > >> i915_gem_object_ggtt_pin_ww() is called without PIN_MAPPABLE. This > >> results in a latency of ~10ms and happens every other vblank/repaint cycle. > >> Therefore, to fix this issue, we try to see if there is space to map > >> at-least two objects of a given size and return early if there isn't. This > >> would ensure that we do not try with PIN_MAPPABLE for any objects that > >> are too big to map thereby preventing unncessary unbind. > >> > >> Testcase: > >> Running Weston and weston-simple-egl on an Alderlake_S (ADLS) platform > >> with a 8K@60 mode results in only ~40 FPS. Since upstream Weston submits > >> a frame ~7ms before the next vblank, the latencies seen between atomic > >> commit and flip event are 7, 24 (7 + 16.66), 7, 24..... suggesting that > >> it misses the vblank every other frame. > >> > >> Here is the ftrace snippet that shows the source of the ~10ms latency: > >> i915_gem_object_pin_to_display_plane() { > >> 0.102 us | i915_gem_object_set_cache_level(); > >> i915_gem_object_ggtt_pin_ww() { > >> 0.390 us | i915_vma_instance(); > >> 0.178 us | i915_vma_misplaced(); > >> i915_vma_unbind() { > >> __i915_active_wait() { > >> 0.082 us | i915_active_acquire_if_busy(); > >> 0.475 us | } > >> intel_runtime_pm_get() { > >> 0.087 us | intel_runtime_pm_acquire(); > >> 0.259 us | } > >> __i915_active_wait() { > >> 0.085 us | i915_active_acquire_if_busy(); > >> 0.240 us | } > >> __i915_vma_evict() { > >> ggtt_unbind_vma() { > >> gen8_ggtt_clear_range() { > >> 10507.255 us | } > >> 10507.689 us | } > >> 10508.516 us | } > >> > >> v2: Instead of using bigjoiner checks, determine whether a scanout > >> buffer is too big by checking to see if it is possible to map > >> two of them into the ggtt. > >> > >> v3 (Ville): > >> - Count how many fb objects can be fit into the available holes > >> instead of checking for a hole twice the object size. > >> - Take alignment constraints into account. > >> - Limit this large scanout buffer check to >= Gen 11 platforms. > >> > >> v4: > >> - Remove existing heuristic that checks just for size. (Ville) > >> - Return early if we find space to map at-least two objects. (Tvrtko) > >> - Slightly update the commit message. > >> > >> v5: (Tvrtko) > >> - Rename the function to indicate that the object may be too big to > >> map into the aperture. > >> - Account for guard pages while calculating the total size required > >> for the object. > >> - Do not subject all objects to the heuristic check and instead > >> consider objects only of a certain size. > >> - Do the hole walk using the rbtree. > >> - Preserve the existing PIN_NONBLOCK logic. > >> - Drop the PIN_MAPPABLE check while pinning the VMA. > >> > >> v6: (Tvrtko) > >> - Return 0 on success and the specific error code on failure to > >> preserve the existing behavior. > >> > >> Cc: Ville Syrjälä > >> Cc: Maarten Lankhorst > >> Cc: Tvrtko Ursulin > >> Cc: Manasi Navare > >> Signed-off-by: Vivek Kasireddy > >> --- > >> drivers/gpu/drm/i915/i915_gem.c | 120 ++++++++++++++++++++++++-------- > >> 1 file changed, 90 insertions(+), 30 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c > >> index e3a2c2a0e156..39f0d17550c3 100644 > >> --- a/drivers/gpu/drm/i915/i915_gem.c > >> +++ b/drivers/gpu/drm/i915/i915_gem.c > >> @@ -46,6 +46,7 @@ > >> #include "gem/i915_gem_mman.h" > >> #include "gem/i915_gem_region.h" > >> #include "gem/i915_gem_userptr.h" > >> +#include "gem/i915_gem_tiling.h" > >> #include "gt/intel_engine_user.h" > >> #include "gt/intel_gt.h" > >> #include "gt/intel_gt_pm.h" > >> @@ -876,6 +877,92 @@ static void discard_ggtt_vma(struct i915_vma *vma) > >> spin_unlock(&obj->vma.lock); > >> } > >> > >> +static int > >> +i915_gem_object_fits_in_aperture(struct drm_i915_gem_object *obj, > >> + u64 alignment, u64 flags) > >> +{ > >> + struct drm_i915_private *i915 = to_i915(obj->base.dev); > >> + struct i915_ggtt *ggtt = to_gt(i915)->ggtt; > >> + struct drm_mm_node *hole; > >> + u64 hole_start, hole_end, start, end; > >> + u64 fence_size, fence_alignment; > >> + unsigned int count = 0; > >> + > >> + /* > >> + * If the required space is larger than the available > >> + * aperture, we will not able to find a slot for the > >> + * object and unbinding the object now will be in > >> + * vain. Worse, doing so may cause us to ping-pong > >> + * the object in and out of the Global GTT and > >> + * waste a lot of cycles under the mutex. > >> + */ > >> + if (obj->base.size > ggtt->mappable_end) > >> + return -E2BIG; > >> + > >> + /* > >> + * If NONBLOCK is set the caller is optimistically > >> + * trying to cache the full object within the mappable > >> + * aperture, and *must* have a fallback in place for > >> + * situations where we cannot bind the object. We > >> + * can be a little more lax here and use the fallback > >> + * more often to avoid costly migrations of ourselves > >> + * and other objects within the aperture. > >> + */ > >> + if (!(flags & PIN_NONBLOCK)) > >> + return 0; > >> + > >> + /* > >> + * We only consider objects whose size is at-least a quarter of > >> + * the aperture to be too big and subject them to the new > >> + * heuristic below. > >> + */ > >> + if (obj->base.size < ggtt->mappable_end / 4) > >> + return 0; > > > > That seems a fairly arbitrary thing to put here. Maybe something the > > caller should check/specify? > > I have no strong opinion on this one. In my mind I categorised it under > "is it a large framebuffer" heuristics. Previously it was less than one > half of aperture always okay, now one quarter, plus 2x hole check if > larger. Both are heuristics. I even mentioned earlier if 2x should be an > input parameter as well, but again, given it's not an exported function > couldn't really justify it. Is there any point in even having this extra check? If we don't think checking this is worth the hassle then why call the function at all? > > > > >> + > >> + if (HAS_GMCH(i915) || DISPLAY_VER(i915) < 11 || > >> + !i915_gem_object_is_framebuffer(obj)) > >> + return 0; > > > > None of that seems appropriate for a generic gem function > > with this name. > > It's not exported though, maybe remove i915_gem prefix to avoid any > ideas of it being generic? These checks don't even seem to doing anything useful. HAS_GMCH should already be covered by always setting PIN_MAPPABLE and hence O_NONBLOCK is never even tried, the pre-icl vs. icl+ check should not exist at all IMO, and if this is only called for framebuffers then why does the code pretend that is not the case? So I would suggest just ditching all these checks, and then the function even does what it says on the tin. -- Ville Syrjälä Intel