[PATCH 11/12] drm/i915: Extend GET_APERTURE ioctl to report available map space

[ankitprasad.r.sharma@intel.com]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

When constructing a batchbuffer, it is sometimes crucial to know the
largest hole into which we can fit a fenceable buffer (for example when
handling very large objects on gen2 and gen3). This depends on the
fragmentation of pinned buffers inside the aperture, a question only the
kernel can easily answer.

This patch extends the current DRM_I915_GEM_GET_APERTURE ioctl to
include a couple of new fields in its reply to userspace - the total
amount of space available in the mappable region of the aperture and
also the single largest block available.

This is not quite what userspace wants to answer the question of whether
this batch will fit as fences are also required to meet severe alignment
constraints within the batch. For this purpose, a third conservative
estimate of largest fence available is also provided. For when userspace
needs more than one batch, we also provide the culmulative space
available for fences such that it has some additional guidance to how
much space it could allocate to fences. Conservatism still wins.

The patch also adds a debugfs file for convenient testing and reporting.

v2: The first object cannot end at offset 0, so we can use last==0 to
detect the empty list.

v3: Expand all values to 64bit, just in case.
    Report total mappable aperture size for userspace that cannot easily
    determine it by inspecting the PCI device.

v4: (Rodrigo) Fixed rebase conflicts.

v5: Keeping limits to get_aperture ioctl, and moved changing numbers to
debugfs, Addressed comments (Chris/Tvrtko)

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c | 133 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem.c     |   1 +
 include/uapi/drm/i915_drm.h         |   5 ++
 3 files changed, 139 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 7f94c6a..d8d7994 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -524,6 +524,138 @@ static int i915_gem_object_info(struct seq_file *m, void* data)
 	return 0;
 }
 
+static int vma_rank_by_ggtt(void *priv,
+			    struct list_head *A,
+			    struct list_head *B)
+{
+	struct i915_vma *a = list_entry(A, typeof(*a), exec_list);
+	struct i915_vma *b = list_entry(B, typeof(*b), exec_list);
+
+	return a->node.start - b->node.start;
+}
+
+static u32 __fence_size(struct drm_i915_private *dev_priv, u32 start, u32 end)
+{
+	u32 size = end - start;
+	u32 fence_size;
+
+	if (INTEL_INFO(dev_priv)->gen < 4) {
+		u32 fence_max;
+		u32 fence_next;
+
+		if (IS_GEN3(dev_priv)) {
+			fence_max = I830_FENCE_MAX_SIZE_VAL << 20;
+			fence_next = 1024*1024;
+		} else {
+			fence_max = I830_FENCE_MAX_SIZE_VAL << 19;
+			fence_next = 512*1024;
+		}
+
+		fence_max = min(fence_max, size);
+		fence_size = 0;
+		/* Find fence_size less than fence_max and power of 2 */
+		while (fence_next <= fence_max) {
+			u32 base = ALIGN(start, fence_next);
+			if (base + fence_next > end)
+				break;
+
+			fence_size = fence_next;
+			fence_next <<= 1;
+		}
+	} else {
+		fence_size = size;
+	}
+
+	return fence_size;
+}
+
+static int i915_gem_aperture_info(struct seq_file *m, void *data)
+{
+	struct drm_info_node *node = m->private;
+	struct drm_device *dev = node->minor->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct i915_ggtt *ggtt = &dev_priv->ggtt;
+	struct drm_i915_gem_get_aperture arg;
+	struct i915_vma *vma;
+	struct list_head map_list;
+	const uint64_t map_limit = ggtt->mappable_end;
+	uint64_t map_space, map_largest, fence_space, fence_largest;
+	uint64_t last, size;
+	int ret;
+
+	INIT_LIST_HEAD(&map_list);
+
+	map_space = map_largest = 0;
+	fence_space = fence_largest = 0;
+
+	ret = i915_gem_get_aperture_ioctl(node->minor->dev, &arg, NULL);
+	if (ret)
+		return ret;
+
+	mutex_lock(&dev->struct_mutex);
+	list_for_each_entry(vma, &ggtt->base.active_list, vm_link)
+		if (vma->pin_count &&
+			(vma->node.start + vma->node.size) <= map_limit)
+			list_add(&vma->exec_list, &map_list);
+	list_for_each_entry(vma, &ggtt->base.inactive_list, vm_link)
+		if (vma->pin_count &&
+			(vma->node.start + vma->node.size) <= map_limit)
+			list_add(&vma->exec_list, &map_list);
+
+	last = 0;
+	list_sort(NULL, &map_list, vma_rank_by_ggtt);
+	while (!list_empty(&map_list)) {
+		vma = list_first_entry(&map_list, typeof(*vma), exec_list);
+		list_del_init(&vma->exec_list);
+
+		if (last == 0)
+			goto skip_first;
+
+		size = vma->node.start - last;
+		if (size > map_largest)
+			map_largest = size;
+		map_space += size;
+
+		size = __fence_size(dev_priv, last, vma->node.start);
+		if (size > fence_largest)
+			fence_largest = size;
+		fence_space += size;
+
+skip_first:
+		last = vma->node.start + vma->node.size;
+	}
+	if (last < map_limit) {
+		size = map_limit - last;
+		if (size > map_largest)
+			map_largest = size;
+		map_space += size;
+
+		size = __fence_size(dev_priv, last, map_limit);
+		if (size > fence_largest)
+			fence_largest = size;
+		fence_space += size;
+	}
+
+	mutex_unlock(&dev->struct_mutex);
+
+	seq_printf(m, "Total size of the GTT: %llu bytes\n",
+		   arg.aper_size);
+	seq_printf(m, "Available space in the GTT: %llu bytes\n",
+		   arg.aper_available_size);
+	seq_printf(m, "Total space in the mappable aperture: %llu bytes\n",
+		   arg.map_total_size);
+	seq_printf(m, "Available space in the mappable aperture: %llu bytes\n",
+		   map_space);
+	seq_printf(m, "Single largest space in the mappable aperture: %llu bytes\n",
+		   map_largest);
+	seq_printf(m, "Available space for fences: %llu bytes\n",
+		   fence_space);
+	seq_printf(m, "Single largest fence available: %llu bytes\n",
+		   fence_largest);
+
+	return 0;
+}
+
 static int i915_gem_gtt_info(struct seq_file *m, void *data)
 {
 	struct drm_info_node *node = m->private;
@@ -5354,6 +5486,7 @@ static int i915_debugfs_create(struct dentry *root,
 static const struct drm_info_list i915_debugfs_list[] = {
 	{"i915_capabilities", i915_capabilities, 0},
 	{"i915_gem_objects", i915_gem_object_info, 0},
+	{"i915_gem_aperture", i915_gem_aperture_info, 0},
 	{"i915_gem_gtt", i915_gem_gtt_info, 0},
 	{"i915_gem_pinned", i915_gem_gtt_info, 0, (void *) PINNED_LIST},
 	{"i915_gem_active", i915_gem_object_list_info, 0, (void *) ACTIVE_LIST},
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 45fd049..a1be35f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -165,6 +165,7 @@ i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
 
 	args->aper_size = ggtt->base.total;
 	args->aper_available_size = args->aper_size - pinned;
+	args->map_total_size = ggtt->mappable_end;;
 
 	return 0;
 }
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index dae02d8..8f38407 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1007,6 +1007,11 @@ struct drm_i915_gem_get_aperture {
 	 * bytes
 	 */
 	__u64 aper_available_size;
+
+	/**
+	 * Total space in the mappable region of the aperture, in bytes
+	 */
+	__u64 map_total_size;
 };
 
 struct drm_i915_get_pipe_from_crtc_id {
-- 
1.9.1

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