[PATCH v2 1/3] drm/i915: Use the MRU stack search after evicting

* [PATCH v2 1/3] drm/i915: Use the MRU stack search after evicting
@ 2017-01-11 11:23 Chris Wilson
  2017-01-11 11:23 ` [PATCH v2 2/3] drm/i915: Extract reserving space in the GTT to a helper Chris Wilson
                   ` (3 more replies)
  0 siblings, 4 replies; 7+ messages in thread
From: Chris Wilson @ 2017-01-11 11:23 UTC (permalink / raw)
  To: intel-gfx

When we evict from the GTT to make room for an object, the hole we
create is put onto the MRU stack inside the drm_mm range manager. On the
next search pass, we can speed up a PIN_HIGH allocation by referencing
that stack for the new hole.

v2: Pull together the 3 identical implements (ahem, a couple were
outdated) into a common routine for allocating a node and evicting as
necessary.
v3: Detect invalid calls to i915_gem_gtt_insert()
v4: kerneldoc

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 drivers/gpu/drm/i915/gvt/aperture_gm.c |  33 +++------
 drivers/gpu/drm/i915/i915_gem_gtt.c    | 121 +++++++++++++++++++++++++++------
 drivers/gpu/drm/i915/i915_gem_gtt.h    |   5 ++
 drivers/gpu/drm/i915/i915_vma.c        |  40 ++---------
 4 files changed, 119 insertions(+), 80 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/aperture_gm.c b/drivers/gpu/drm/i915/gvt/aperture_gm.c
index 016227d77dd4..a97d56ea3d83 100644
--- a/drivers/gpu/drm/i915/gvt/aperture_gm.c
+++ b/drivers/gpu/drm/i915/gvt/aperture_gm.c
@@ -41,47 +41,34 @@ static int alloc_gm(struct intel_vgpu *vgpu, bool high_gm)
 {
 	struct intel_gvt *gvt = vgpu->gvt;
 	struct drm_i915_private *dev_priv = gvt->dev_priv;
-	u32 alloc_flag, search_flag;
+	unsigned int flags;
 	u64 start, end, size;
 	struct drm_mm_node *node;
-	int retried = 0;
 	int ret;
 
 	if (high_gm) {
-		search_flag = DRM_MM_SEARCH_BELOW;
-		alloc_flag = DRM_MM_CREATE_TOP;
 		node = &vgpu->gm.high_gm_node;
 		size = vgpu_hidden_sz(vgpu);
 		start = gvt_hidden_gmadr_base(gvt);
 		end = gvt_hidden_gmadr_end(gvt);
+		flags = PIN_HIGH;
 	} else {
-		search_flag = DRM_MM_SEARCH_DEFAULT;
-		alloc_flag = DRM_MM_CREATE_DEFAULT;
 		node = &vgpu->gm.low_gm_node;
 		size = vgpu_aperture_sz(vgpu);
 		start = gvt_aperture_gmadr_base(gvt);
 		end = gvt_aperture_gmadr_end(gvt);
+		flags = PIN_MAPPABLE;
 	}
 
 	mutex_lock(&dev_priv->drm.struct_mutex);
-search_again:
-	ret = drm_mm_insert_node_in_range_generic(&dev_priv->ggtt.base.mm,
-						  node, size, 4096,
-						  I915_COLOR_UNEVICTABLE,
-						  start, end, search_flag,
-						  alloc_flag);
-	if (ret) {
-		ret = i915_gem_evict_something(&dev_priv->ggtt.base,
-					       size, 4096,
-					       I915_COLOR_UNEVICTABLE,
-					       start, end, 0);
-		if (ret == 0 && ++retried < 3)
-			goto search_again;
-
-		gvt_err("fail to alloc %s gm space from host, retried %d\n",
-				high_gm ? "high" : "low", retried);
-	}
+	ret = i915_gem_gtt_insert(&dev_priv->ggtt.base, node,
+				  size, 4096, I915_COLOR_UNEVICTABLE,
+				  start, end, flags);
 	mutex_unlock(&dev_priv->drm.struct_mutex);
+	if (ret)
+		gvt_err("fail to alloc %s gm space from host\n",
+			high_gm ? "high" : "low");
+
 	return ret;
 }
 
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 8aca11f5f446..136f90ba95ab 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -23,10 +23,13 @@
  *
  */
 
+#include <linux/log2.h>
 #include <linux/seq_file.h>
 #include <linux/stop_machine.h>
+
 #include <drm/drmP.h>
 #include <drm/i915_drm.h>
+
 #include "i915_drv.h"
 #include "i915_vgpu.h"
 #include "i915_trace.h"
@@ -2032,7 +2035,6 @@ static int gen6_ppgtt_allocate_page_directories(struct i915_hw_ppgtt *ppgtt)
 	struct i915_address_space *vm = &ppgtt->base;
 	struct drm_i915_private *dev_priv = ppgtt->base.i915;
 	struct i915_ggtt *ggtt = &dev_priv->ggtt;
-	bool retried = false;
 	int ret;
 
 	/* PPGTT PDEs reside in the GGTT and consists of 512 entries. The
@@ -2045,29 +2047,14 @@ static int gen6_ppgtt_allocate_page_directories(struct i915_hw_ppgtt *ppgtt)
 	if (ret)
 		return ret;
 
-alloc:
-	ret = drm_mm_insert_node_in_range_generic(&ggtt->base.mm, &ppgtt->node,
-						  GEN6_PD_SIZE, GEN6_PD_ALIGN,
-						  I915_COLOR_UNEVICTABLE,
-						  0, ggtt->base.total,
-						  DRM_MM_TOPDOWN);
-	if (ret == -ENOSPC && !retried) {
-		ret = i915_gem_evict_something(&ggtt->base,
-					       GEN6_PD_SIZE, GEN6_PD_ALIGN,
-					       I915_COLOR_UNEVICTABLE,
-					       0, ggtt->base.total,
-					       0);
-		if (ret)
-			goto err_out;
-
-		retried = true;
-		goto alloc;
-	}
-
+	ret = i915_gem_gtt_insert(&ggtt->base, &ppgtt->node,
+				  GEN6_PD_SIZE, GEN6_PD_ALIGN,
+				  I915_COLOR_UNEVICTABLE,
+				  0, ggtt->base.total,
+				  PIN_HIGH);
 	if (ret)
 		goto err_out;
 
-
 	if (ppgtt->node.start < ggtt->mappable_end)
 		DRM_DEBUG("Forced to use aperture for PDEs\n");
 
@@ -3567,3 +3554,95 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
 	return ret;
 }
 
+/**
+ * i915_gem_gtt_insert - insert a node into an address_space (GTT)
+ * @vm - the &struct i915_address_space
+ * @node - the @struct drm_mm_node (typicallay i915_vma.mode)
+ * @size - how much space to allocate inside the GTT,
+ *         must be #I915_GTT_PAGE_SIZE aligned
+ * @alignment - required alignment of starting offset, may be 0 but
+ *              if specified, this must be a power-of-two and at least
+ *              #I915_GTT_MIN_ALIGNMENT
+ * @color - color to apply to node
+ * @start - start of any range restriction inside GTT (0 for all),
+ *          must be #I915_GTT_PAGE_SIZE aligned
+ * @end - end of any range restriction inside GTT (U64_MAX for all),
+ *        must be #I915_GTT_PAGE_SIZE aligned
+ * @flags - control search and eviction behaviour
+ *
+ * i915_gem_gtt_insert() first searches for an available hole into which
+ * is can insert the node. The hole address is aligned to @alignment and
+ * its @size must then fit entirely within the [@start, @end] bounds. The
+ * nodes on either side of the hole must match @color, or else a guard page
+ * will be inserted between the two nodes (or the node evicted). If no
+ * suitable hole is found, then the LRU list of objects within the GTT
+ * is scanned to find the first set of replacement nodes to create the hole.
+ * Those old overlapping nodes are evicted from the GTT (and so must be
+ * rebound before any future use). Any node that is current pinned cannot
+ * be evicted (see i915_vma_pin()). Similar if the node's VMA is currently
+ * active and #PIN_NONBLOCK is specified, that node is also skipped when
+ * searching for an eviction candidate. See i915_gem_evict_something() for
+ * the gory details on the eviction algorithm.
+ *
+ * Returns: 0 on success, -ENOSPC if no suitable hole is found, -EINTR if
+ * asked to wait for eviction and interrupted.
+ */
+int i915_gem_gtt_insert(struct i915_address_space *vm,
+			struct drm_mm_node *node,
+			u64 size, u64 alignment, unsigned long color,
+			u64 start, u64 end, unsigned int flags)
+{
+	u32 search_flag, alloc_flag;
+	int err;
+
+	lockdep_assert_held(&vm->i915->drm.struct_mutex);
+	GEM_BUG_ON(!size);
+	GEM_BUG_ON(!IS_ALIGNED(size, I915_GTT_PAGE_SIZE));
+	GEM_BUG_ON(alignment && !is_power_of_2(alignment));
+	GEM_BUG_ON(alignment && !IS_ALIGNED(alignment, I915_GTT_MIN_ALIGNMENT));
+	GEM_BUG_ON(start >= end);
+	GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
+	GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));
+
+	if (unlikely(range_overflows(start, size, end)))
+		return -ENOSPC;
+
+	if (unlikely(round_up(start, alignment) > round_down(end - size, alignment)))
+		return -ENOSPC;
+
+	if (flags & PIN_HIGH) {
+		search_flag = DRM_MM_SEARCH_BELOW;
+		alloc_flag = DRM_MM_CREATE_TOP;
+	} else {
+		search_flag = DRM_MM_SEARCH_DEFAULT;
+		alloc_flag = DRM_MM_CREATE_DEFAULT;
+	}
+
+	/* We only allocate in PAGE_SIZE/GTT_PAGE_SIZE (4096) chunks,
+	 * so we know that we always have a minimum alignment of 4096.
+	 * The drm_mm range manager is optimised to return results
+	 * with zero alignment, so where possible use the optimal
+	 * path.
+	 */
+	GEM_BUG_ON(size & (I915_GTT_MIN_ALIGNMENT - 1));
+	if (alignment <= I915_GTT_MIN_ALIGNMENT)
+		alignment = 0;
+
+	err = drm_mm_insert_node_in_range_generic(&vm->mm, node,
+						  size, alignment, color,
+						  start, end,
+						  search_flag, alloc_flag);
+	if (err != -ENOSPC)
+		return err;
+
+	err = i915_gem_evict_something(vm, size, alignment, color,
+				       start, end, flags);
+	if (err)
+		return err;
+
+	search_flag = DRM_MM_SEARCH_DEFAULT;
+	return drm_mm_insert_node_in_range_generic(&vm->mm, node,
+						   size, alignment, color,
+						   start, end,
+						   search_flag, alloc_flag);
+}
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 34a4fd560fa2..79198352a491 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -532,6 +532,11 @@ int __must_check i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj,
 void i915_gem_gtt_finish_pages(struct drm_i915_gem_object *obj,
 			       struct sg_table *pages);
 
+int i915_gem_gtt_insert(struct i915_address_space *vm,
+			struct drm_mm_node *node,
+			u64 size, u64 alignment, unsigned long color,
+			u64 start, u64 end, unsigned int flags);
+
 /* Flags used by pin/bind&friends. */
 #define PIN_NONBLOCK		BIT(0)
 #define PIN_MAPPABLE		BIT(1)
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 490914f89663..df3750d4c907 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -431,43 +431,11 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 				goto err_unpin;
 		}
 	} else {
-		u32 search_flag, alloc_flag;
-
-		if (flags & PIN_HIGH) {
-			search_flag = DRM_MM_SEARCH_BELOW;
-			alloc_flag = DRM_MM_CREATE_TOP;
-		} else {
-			search_flag = DRM_MM_SEARCH_DEFAULT;
-			alloc_flag = DRM_MM_CREATE_DEFAULT;
-		}
-
-		/* We only allocate in PAGE_SIZE/GTT_PAGE_SIZE (4096) chunks,
-		 * so we know that we always have a minimum alignment of 4096.
-		 * The drm_mm range manager is optimised to return results
-		 * with zero alignment, so where possible use the optimal
-		 * path.
-		 */
-		if (alignment <= I915_GTT_MIN_ALIGNMENT)
-			alignment = 0;
-
-search_free:
-		ret = drm_mm_insert_node_in_range_generic(&vma->vm->mm,
-							  &vma->node,
-							  size, alignment,
-							  obj->cache_level,
-							  start, end,
-							  search_flag,
-							  alloc_flag);
-		if (ret) {
-			ret = i915_gem_evict_something(vma->vm, size, alignment,
-						       obj->cache_level,
-						       start, end,
-						       flags);
-			if (ret == 0)
-				goto search_free;
-
+		ret = i915_gem_gtt_insert(vma->vm, &vma->node,
+					  size, alignment, obj->cache_level,
+					  start, end, flags);
+		if (ret)
 			goto err_unpin;
-		}
 
 		GEM_BUG_ON(vma->node.start < start);
 		GEM_BUG_ON(vma->node.start + vma->node.size > end);
-- 
2.11.0

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