Re: [PATCH 46/48] drm: Optionally create mm blocks from top-to-bottom

David Herrmann
2013-12-08T14:28:04Z

Hi

On Fri, Dec 6, 2013 at 11:11 PM, Ben Widawsky
<benjamin.widawsky@intel.com> wrote:
> From: Chris Wilson <chris@chris-wilson.co.uk>
>
> Clients like i915 needs to segregate cache domains within the GTT which
> can lead to small amounts of fragmentation. By allocating the uncached
> buffers from the bottom and the cacheable buffers from the top, we can
> reduce the amount of wasted space and also optimize allocation of the
> mappable portion of the GTT to only those buffers that require CPU
> access through the GTT.
>
> v2 by Ben:
> Update callers in i915_gem_object_bind_to_gtt()
> Turn search flags and allocation flags into separate enums
> Make checkpatch happy where logical/easy
>
> v3 by Ben:
> Rebased on top of the many drm_mm changes since the original patches
> Remove ATOMIC from allocator flags (Chris)
> Reverse order of TOPDOWN and BOTTOMUP

CC'ing dri-devel as I'm not subscribed to intel-gfx.

> Cc: David Herrmann <dh.herrmann@gmail.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/drm_mm.c | 56 +++++++++++++++++++++++++++----------
> drivers/gpu/drm/i915/i915_gem.c | 3 +-
> drivers/gpu/drm/i915/i915_gem_gtt.c | 2 +-
> include/drm/drm_mm.h | 29 ++++++++++++++++---
> 4 files changed, 69 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index af93cc5..4f5e4f6 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -65,7 +65,8 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
> static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
> struct drm_mm_node *node,
> unsigned long size, unsigned alignment,
> - unsigned long color)
> + unsigned long color,
> + enum drm_mm_allocator_flags flags)
> {
> struct drm_mm *mm = hole_node->mm;
> unsigned long hole_start = drm_mm_hole_node_start(hole_node);
> @@ -78,12 +79,22 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
> if (mm->color_adjust)
> mm->color_adjust(hole_node, color, &adj_start, &adj_end);
>
> + if (flags & DRM_MM_CREATE_TOP)
> + adj_start = adj_end - size;
> +

That should be above the call to mm->color_adjust(), imo. But I'm not
entirely sure what kind of adjustments drivers do. At least you should
be consistend with the range-helper below where you call it *before*
the color-adjustment.

> if (alignment) {
> unsigned tmp = adj_start % alignment;
> - if (tmp)
> - adj_start += alignment - tmp;
> + if (tmp) {
> + if (flags & DRM_MM_CREATE_TOP)
> + adj_start -= tmp;
> + else
> + adj_start += alignment - tmp;
> + }
> }
>
> + BUG_ON(adj_start < hole_start);
> + BUG_ON(adj_end > hole_end);
> +
> if (adj_start == hole_start) {
> hole_node->hole_follows = 0;
> list_del(&hole_node->hole_stack);
> @@ -155,16 +166,17 @@ EXPORT_SYMBOL(drm_mm_reserve_node);
> int drm_mm_insert_node_generic(struct drm_mm *mm, struct drm_mm_node *node,
> unsigned long size, unsigned alignment,
> unsigned long color,
> - enum drm_mm_search_flags flags)
> + enum drm_mm_search_flags sflags,
> + enum drm_mm_allocator_flags aflags)
> {
> struct drm_mm_node *hole_node;
>
> hole_node = drm_mm_search_free_generic(mm, size, alignment,
> - color, flags);
> + color, sflags);
> if (!hole_node)
> return -ENOSPC;
>
> - drm_mm_insert_helper(hole_node, node, size, alignment, color);
> + drm_mm_insert_helper(hole_node, node, size, alignment, color, aflags);
> return 0;
> }
> EXPORT_SYMBOL(drm_mm_insert_node_generic);
> @@ -173,7 +185,8 @@ static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
> struct drm_mm_node *node,
> unsigned long size, unsigned alignment,
> unsigned long color,
> - unsigned long start, unsigned long end)
> + unsigned long start, unsigned long end,
> + enum drm_mm_allocator_flags flags)
> {
> struct drm_mm *mm = hole_node->mm;
> unsigned long hole_start = drm_mm_hole_node_start(hole_node);
> @@ -188,13 +201,20 @@ static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
> if (adj_end > end)
> adj_end = end;
>
> + if (flags & DRM_MM_CREATE_TOP)
> + adj_start = adj_end - size;
> +
> if (mm->color_adjust)
> mm->color_adjust(hole_node, color, &adj_start, &adj_end);
>
> if (alignment) {
> unsigned tmp = adj_start % alignment;
> - if (tmp)
> - adj_start += alignment - tmp;
> + if (tmp) {
> + if (flags & DRM_MM_CREATE_TOP)
> + adj_start -= tmp;
> + else
> + adj_start += alignment - tmp;
> + }
> }
>
> if (adj_start == hole_start) {
> @@ -211,6 +231,8 @@ static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
> INIT_LIST_HEAD(&node->hole_stack);
> list_add(&node->node_list, &hole_node->node_list);
>
> + BUG_ON(node->start < start);
> + BUG_ON(node->start < adj_start);
> BUG_ON(node->start + node->size > adj_end);
> BUG_ON(node->start + node->size > end);
>
> @@ -227,21 +249,23 @@ static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
> * restricted allocations. The preallocated memory node must be cleared.
> */
> int drm_mm_insert_node_in_range_generic(struct drm_mm *mm, struct drm_mm_node *node,
> - unsigned long size, unsigned alignment, unsigned long color,
> + unsigned long size, unsigned alignment,
> + unsigned long color,
> unsigned long start, unsigned long end,
> - enum drm_mm_search_flags flags)
> + enum drm_mm_search_flags sflags,
> + enum drm_mm_allocator_flags aflags)
> {
> struct drm_mm_node *hole_node;
>
> hole_node = drm_mm_search_free_in_range_generic(mm,
> size, alignment, color,
> - start, end, flags);
> + start, end, sflags);
> if (!hole_node)
> return -ENOSPC;
>
> drm_mm_insert_helper_range(hole_node, node,
> size, alignment, color,
> - start, end);
> + start, end, aflags);
> return 0;
> }
> EXPORT_SYMBOL(drm_mm_insert_node_in_range_generic);
> @@ -315,7 +339,8 @@ static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
> best = NULL;
> best_size = ~0UL;
>
> - drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
> + __drm_mm_for_each_hole(entry, mm, adj_start, adj_end,
> + flags & DRM_MM_SEARCH_BELOW) {
> if (mm->color_adjust) {
> mm->color_adjust(entry, color, &adj_start, &adj_end);
> if (adj_end <= adj_start)
> @@ -356,7 +381,8 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
> best = NULL;
> best_size = ~0UL;
>
> - drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
> + __drm_mm_for_each_hole(entry, mm, adj_start, adj_end,
> + flags & DRM_MM_SEARCH_BELOW) {
> if (adj_start < start)
> adj_start = start;
> if (adj_end > end)
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index a03c262..1360f89 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3280,7 +3280,8 @@ search_free:
> ret = drm_mm_insert_node_in_range_generic(&vm->mm, &vma->node,
> size, alignment,
> obj->cache_level, 1, gtt_max,
> - DRM_MM_SEARCH_DEFAULT);
> + DRM_MM_SEARCH_DEFAULT,
> + DRM_MM_CREATE_DEFAULT);
> if (ret) {
> ret = i915_gem_evict_something(dev, vm, size, alignment,
> obj->cache_level,
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 998f9a0..37832e4 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -861,7 +861,7 @@ alloc:
> &ppgtt->node, GEN6_PD_SIZE,
> GEN6_PD_ALIGN, 0,
> 0, dev_priv->gtt.base.total,
> - DRM_MM_SEARCH_DEFAULT);
> + DRM_MM_BOTTOMUP);
> if (ret == -ENOSPC && !retried) {
> ret = i915_gem_evict_something(dev, &dev_priv->gtt.base,
> GEN6_PD_SIZE, GEN6_PD_ALIGN,
> diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
> index cba6786..36c1d8f 100644
> --- a/include/drm/drm_mm.h
> +++ b/include/drm/drm_mm.h
> @@ -47,8 +47,17 @@
> enum drm_mm_search_flags {
> DRM_MM_SEARCH_DEFAULT = 0,
> DRM_MM_SEARCH_BEST = 1 << 0,
> + DRM_MM_SEARCH_BELOW = 1 << 1,

SEARCH_BEST and SEARCH_BELOW are (almost) mutually exclusive, right?
Hm, but doesn't really hurt if someone specifies both so should be
fine.

Regarding the names: Something like DRM_MM_SEARCH_FROM_TOP sounds
better to my German ears, but what do I know.. (same below for
CREATE_TOP->CREATE_FROM_TOP).

> };
>
> +enum drm_mm_allocator_flags {
> + DRM_MM_CREATE_DEFAULT = 0,
> + DRM_MM_CREATE_TOP = 1 << 0,
> +};
> +
> +#define DRM_MM_BOTTOMUP DRM_MM_SEARCH_DEFAULT, DRM_MM_CREATE_DEFAULT
> +#define DRM_MM_TOPDOWN DRM_MM_SEARCH_BELOW, DRM_MM_CREATE_TOP
> +

That is ugly. Is that really needed? The drm_mm calls already have a
lot of arguments, I don't think we should hide the extra flag just to
save one. If it's about the more obvious name, why not add "static
inline" helpers? debuggers hate pre-processor magic..

Apart from the adjust_color() thing, I'm fine with this patch whether
you change names/arguments or not. So with that fixed:
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>

Thanks
David

> struct drm_mm_node {
> struct list_head node_list;
> struct list_head hole_stack;
> @@ -133,6 +142,14 @@ static inline unsigned long drm_mm_hole_node_end(struct drm_mm_node *hole_node)
> 1 : 0; \
> entry = list_entry(entry->hole_stack.next, struct drm_mm_node, hole_stack))
>
> +#define __drm_mm_for_each_hole(entry, mm, hole_start, hole_end, backwards) \
> + for (entry = list_entry((backwards) ? (mm)->hole_stack.prev : (mm)->hole_stack.next, struct drm_mm_node, hole_stack); \
> + &entry->hole_stack != &(mm)->hole_stack ? \
> + hole_start = drm_mm_hole_node_start(entry), \
> + hole_end = drm_mm_hole_node_end(entry), \
> + 1 : 0; \
> + entry = list_entry((backwards) ? entry->hole_stack.prev : entry->hole_stack.next, struct drm_mm_node, hole_stack))
> +
> /*
> * Basic range manager support (drm_mm.c)
> */
> @@ -143,14 +160,16 @@ extern int drm_mm_insert_node_generic(struct drm_mm *mm,
> unsigned long size,
> unsigned alignment,
> unsigned long color,
> - enum drm_mm_search_flags flags);
> + enum drm_mm_search_flags sflags,
> + enum drm_mm_allocator_flags aflags);
> static inline int drm_mm_insert_node(struct drm_mm *mm,
> struct drm_mm_node *node,
> unsigned long size,
> unsigned alignment,
> enum drm_mm_search_flags flags)
> {
> - return drm_mm_insert_node_generic(mm, node, size, alignment, 0, flags);
> + return drm_mm_insert_node_generic(mm, node, size, alignment, 0, flags,
> + DRM_MM_CREATE_DEFAULT);
> }
>
> extern int drm_mm_insert_node_in_range_generic(struct drm_mm *mm,
> @@ -160,7 +179,8 @@ extern int drm_mm_insert_node_in_range_generic(struct drm_mm *mm,
> unsigned long color,
> unsigned long start,
> unsigned long end,
> - enum drm_mm_search_flags flags);
> + enum drm_mm_search_flags sflags,
> + enum drm_mm_allocator_flags aflags);
> static inline int drm_mm_insert_node_in_range(struct drm_mm *mm,
> struct drm_mm_node *node,
> unsigned long size,
> @@ -170,7 +190,8 @@ static inline int drm_mm_insert_node_in_range(struct drm_mm *mm,
> enum drm_mm_search_flags flags)
> {
> return drm_mm_insert_node_in_range_generic(mm, node, size, alignment,
> - 0, start, end, flags);
> + 0, start, end, flags,
> + DRM_MM_CREATE_DEFAULT);
> }
>
> extern void drm_mm_remove_node(struct drm_mm_node *node);
> --
> 1.8.4.2
>