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 99F6CC433F5 for ; Thu, 17 Mar 2022 11:16:23 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0B7DF10E89B; Thu, 17 Mar 2022 11:16:23 +0000 (UTC) Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2577E10E7E3 for ; Thu, 17 Mar 2022 11:16:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1647515781; x=1679051781; h=message-id:date:mime-version:subject:to:references:from: cc:in-reply-to:content-transfer-encoding; bh=SI0FKO7I6S8olgwAftOrDDcOopEWmCnUPdpmcvchXsc=; b=jqbxjX7XyHSuTEfSQ3Dj9Me2R1964SylbSkEpilax+1tyWn3IPn4Ko2D QaEzpeiEUJ7z8NYoxhUhDtY4Bnt4TcgDagEMyI6zT0U+zra8JtqXbW5SR R+ux6or0RQl01kXhPH5VMaubw/bkiiF9XP/HySFRFnDCvjEyjwZA8QXeT yQkN0PUfF2sMXqnfAitum9iMFXD/9luWSIo6+DAaetWeLzWqebHyhys4S zkoRL5njH1WSX69+k6cES4g2MNItLTNNOpdK1ihmMAFg2cuRoCqVzfOMw ABIvFz86gpbKS9RcVHTpCx7PYeqGS9u22V6fBdxta3b+V0D9gsgGWb7rP Q==; X-IronPort-AV: E=McAfee;i="6200,9189,10288"; a="237452259" X-IronPort-AV: E=Sophos;i="5.90,188,1643702400"; d="scan'208";a="237452259" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2022 04:16:20 -0700 X-IronPort-AV: E=Sophos;i="5.90,188,1643702400"; d="scan'208";a="516727085" Received: from liujoann-mobl.amr.corp.intel.com (HELO [10.209.162.134]) ([10.209.162.134]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2022 04:16:18 -0700 Message-ID: Date: Thu, 17 Mar 2022 11:16:15 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: Vivek Kasireddy , intel-gfx@lists.freedesktop.org References: <20220317072333.1048130-1-vivek.kasireddy@intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc In-Reply-To: <20220317072333.1048130-1-vivek.kasireddy@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Intel-gfx] [PATCH v1] drm/i915/gem: Don't evict unmappable VMAs when pinning with PIN_MAPPABLE 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 17/03/2022 07:23, 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 -- because there is no space for it in the aperture -- > 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 whole > thing results in a latency of ~10ms and happens every other repaint cycle. Just out of curiosity - have you looked at where does this 10ms come from? Like is it simply clearing/writing PTEs so expensive, or there is more to it? Apologies if I asked this before.. > Therefore, to fix this issue, we just ensure that the misplaced VMA > does not get evicted when we try to pin it with PIN_MAPPABLE -- by > returning early if the mappable/fenceable flag is not set. > > Testcase: > Running Weston and weston-simple-egl on an Alderlake_S (ADLS) platform > with a 8K@60 mode results in only ~40 FPS (compared to ~59 FPS with > this patch). 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 | } > > Cc: Tvrtko Ursulin > Signed-off-by: Vivek Kasireddy > --- > drivers/gpu/drm/i915/i915_gem.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c > index 9747924cc57b..7307c5de1c58 100644 > --- a/drivers/gpu/drm/i915/i915_gem.c > +++ b/drivers/gpu/drm/i915/i915_gem.c > @@ -939,8 +939,14 @@ i915_gem_object_ggtt_pin_ww(struct drm_i915_gem_object *obj, > if (i915_vma_is_pinned(vma) || i915_vma_is_active(vma)) > return ERR_PTR(-ENOSPC); > > + /* > + * If this misplaced vma is too big (i.e, at-least > + * half the size of aperture) or just unmappable, > + * we would not be able to pin with PIN_MAPPABLE. > + */ I would be tempted to describe the ping-pong issue in the comment. In short would do it, but just because git blame on a line of code tends to fail to lead to the correct commit message after a while. So maybe just say along the lines of "If the misplaced vma is too big ... or hasn't been pinned mappable before, we ignore the misplacement when PIN_NONBLOCK is set in order to avoid ping-pong of double (or more) -buffered frame buffers into the aperture and out on every vblank." > if (flags & PIN_MAPPABLE && > - vma->fence_size > ggtt->mappable_end / 2) > + (vma->fence_size > ggtt->mappable_end / 2 || > + !i915_vma_is_map_and_fenceable(vma))) > return ERR_PTR(-ENOSPC); > } > With the expanded comment it looks good to me. Reviewed-by: Tvrtko Ursulin + Daniel if he wants to double check it. Regards, Tvrtko