[Intel-gfx] [PATCH 3/3] drm/i915: Allocate active tracking nodes from a slabcache

[Chris Wilson]

Wrap the active tracking for a GPU references in a slabcache for faster
allocations, and hopefully better fragmentation reduction.

v3: Nothing device specific left, it's just a slabcache that we can
make global.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_active.c | 31 +++++++++++++++++++++++++++---
 drivers/gpu/drm/i915/i915_active.h |  3 +++
 drivers/gpu/drm/i915/i915_pci.c    |  3 +++
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index b1fefe98f9a6..5818ddf88462 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -9,6 +9,17 @@
 
 #define BKL(ref) (&(ref)->i915->drm.struct_mutex)
 
+/*
+ * Active refs memory management
+ *
+ * To be more economical with memory, we reap all the i915_active trees as
+ * they idle (when we know the active requests are inactive) and allocate the
+ * nodes from a local slab cache to hopefully reduce the fragmentation.
+ */
+static struct i915_global_active {
+	struct kmem_cache *slab_cache;
+} global;
+
 struct active_node {
 	struct i915_gem_active base;
 	struct i915_active *ref;
@@ -23,7 +34,7 @@ __active_park(struct i915_active *ref)
 
 	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 		GEM_BUG_ON(i915_gem_active_isset(&it->base));
-		kfree(it);
+		kmem_cache_free(global.slab_cache, it);
 	}
 	ref->tree = RB_ROOT;
 }
@@ -96,11 +107,11 @@ active_instance(struct i915_active *ref, u64 idx)
 			p = &parent->rb_left;
 	}
 
-	node = kmalloc(sizeof(*node), GFP_KERNEL);
+	node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
 
 	/* kmalloc may retire the ref->last (thanks shrinker)! */
 	if (unlikely(!i915_gem_active_raw(&ref->last, BKL(ref)))) {
-		kfree(node);
+		kmem_cache_free(global.slab_cache, node);
 		goto out;
 	}
 
@@ -234,6 +245,20 @@ void i915_active_fini(struct i915_active *ref)
 	GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
 	GEM_BUG_ON(ref->count);
 }
+
+int __init i915_global_active_init(void)
+{
+	global.slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
+	if (!global.slab_cache)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void __exit i915_global_active_exit(void)
+{
+	kmem_cache_destroy(global.slab_cache);
+}
 #endif
 
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
index 6130c6770d10..48fdb1497883 100644
--- a/drivers/gpu/drm/i915/i915_active.h
+++ b/drivers/gpu/drm/i915/i915_active.h
@@ -63,4 +63,7 @@ void i915_active_fini(struct i915_active *ref);
 static inline void i915_active_fini(struct i915_active *ref) { }
 #endif
 
+int i915_global_active_init(void);
+void i915_global_active_exit(void);
+
 #endif /* _I915_ACTIVE_H_ */
diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index 44c23ac60347..751a787c83d1 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -793,6 +793,8 @@ static int __init i915_init(void)
 	bool use_kms = true;
 	int err;
 
+	i915_global_active_init();
+
 	err = i915_mock_selftests();
 	if (err)
 		return err > 0 ? 0 : err;
@@ -824,6 +826,7 @@ static void __exit i915_exit(void)
 		return;
 
 	pci_unregister_driver(&i915_pci_driver);
+	i915_global_active_exit();
 }
 
 module_init(i915_init);
-- 
2.20.1