On Mon, Sep 15, 2014 at 01:33:44PM +0100, Chris Wilson wrote:
> 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.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_debugfs.c | 28 +++++++++
> drivers/gpu/drm/i915/i915_gem.c | 111 ++++++++++++++++++++++++++++++++++--
> include/uapi/drm/i915_drm.h | 20 +++++++
> 3 files changed, 155 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 9e63ccbea52e..41d92f29aef1 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -534,6 +534,33 @@ static int obj_rank_by_ggtt(void *priv, struct list_head *A, struct list_head *B
> return i915_gem_obj_ggtt_offset(a) - i915_gem_obj_ggtt_offset(b);
> }
>
> +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_gem_get_aperture arg;
> + int ret;
> +
> + ret = i915_gem_get_aperture_ioctl(dev, &arg, NULL);
> + if (ret)
> + return ret;
> +
> + 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, "Available space in the mappable aperture: %u bytes\n",
> + arg.map_available_size);
> + seq_printf(m, "Single largest space in the mappable aperture: %u bytes\n",
> + arg.map_largest_size);
> + seq_printf(m, "Available space for fences: %u bytes\n",
> + arg.fence_available_size);
> + seq_printf(m, "Single largest fence available: %u bytes\n",
> + arg.fence_largest_size);
> +
> + return 0;
> +}
> +
> static int i915_gem_gtt_info(struct seq_file *m, void *data)
> {
> struct drm_info_node *node = m->private;
> @@ -4198,6 +4225,7 @@ 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 4b9de297b967..4b75086a1dc9 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -31,6 +31,7 @@
> #include "i915_drv.h"
> #include "i915_trace.h"
> #include "intel_drv.h"
> +#include <linux/list_sort.h>
> #include <linux/oom.h>
> #include <linux/shmem_fs.h>
> #include <linux/slab.h>
> @@ -260,6 +261,49 @@ i915_gem_init_ioctl(struct drm_device *dev, void *data,
> return 0;
> }
>
> +static int obj_rank_by_ggtt(void *priv,
> + struct list_head *A,
> + struct list_head *B)
> +{
> + struct drm_i915_gem_object *a = list_entry(A,typeof(*a), obj_exec_link);
> + struct drm_i915_gem_object *b = list_entry(B,typeof(*b), obj_exec_link);
> +
> + return i915_gem_obj_ggtt_offset(a) - i915_gem_obj_ggtt_offset(b);
> +}
> +
> +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;
> + 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;
> +}
> +
> int
> i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
> struct drm_file *file)
> @@ -267,17 +311,76 @@ i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
> struct drm_i915_private *dev_priv = dev->dev_private;
> struct drm_i915_gem_get_aperture *args = data;
> struct drm_i915_gem_object *obj;
> - size_t pinned;
> + struct list_head map_list;
> + const u32 map_limit = dev_priv->gtt.mappable_end;
> + size_t pinned, map_space, map_largest, fence_space, fence_largest;
> + u32 last, size;
> +
> + INIT_LIST_HEAD(&map_list);
>
> pinned = 0;
> + map_space = map_largest = 0;
> + fence_space = fence_largest = 0;
> +
> mutex_lock(&dev->struct_mutex);
> - list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list)
> - if (i915_gem_obj_is_pinned(obj))
> - pinned += i915_gem_obj_ggtt_size(obj);
> + list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list) {
> + struct i915_vma *vma = i915_gem_obj_to_ggtt(obj);
> +
> + if (vma == NULL || !vma->pin_count)
> + continue;
> +
> + pinned += vma->node.size;
> +
> + if (vma->node.start < map_limit)
> + list_add(&obj->obj_exec_link, &map_list);
> + }
> +
> + last = ~0;
> + list_sort(NULL, &map_list, obj_rank_by_ggtt);
> + while (!list_empty(&map_list)) {
> + struct i915_vma *vma;
> +
> + obj = list_first_entry(&map_list, typeof(*obj), obj_exec_link);
> + list_del_init(&obj->obj_exec_link);
> +
> + vma = i915_gem_obj_to_ggtt(obj);
> + 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 == ~0U)
> + last = 0;
> + 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);
>
> args->aper_size = dev_priv->gtt.base.total;
> args->aper_available_size = args->aper_size - pinned;
> + args->map_available_size = map_space;
> + args->map_largest_size = map_largest;
> + args->fence_available_size = fence_space;
> + args->fence_largest_size = fence_largest;
>
> return 0;
> }
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 422513ba9e59..35308691cf8d 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -941,6 +941,26 @@ struct drm_i915_gem_get_aperture {
> * bytes
> */
> __u64 aper_available_size;
> +
> + /**
> + * Available space in the mappable region of the aperture, in bytes
> + */
> + __u32 map_available_size;
> +
> + /**
> + * Single largest available region inside the mappable region, in bytes.
> + */
> + __u32 map_largest_size;
> +
> + /**
> + * Culmulative space available for fences, in bytes
> + */
> + __u32 fence_available_size;
> +
> + /**
> + * Single largest fenceable region, in bytes.
> + */
> + __u32 fence_largest_size;
> };
So what will happen when old usermode program (with short old structure)
calls the ioctl ? I believe the memory which happens to be located
after the structure is corrupted, or am I missing some magic there ?
I.e., the question is why this patch does not break the ABI.
>
> struct drm_i915_get_pipe_from_crtc_id {
> --
> 2.1.0
>
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