drm/i915: Allocate active tracking nodes from a slabcache

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.
v4: Include i915_active.h and don't put the initfunc under DEBUG_GEM

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190205130005.2807-4-chris@chris-wilson.co.uk

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;
 	}
 
@@ -239,3 +250,17 @@ void i915_active_fini(struct i915_active *ref)
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/i915_active.c"
 #endif
+
+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);
+}

drivers/gpu/drm/i915/i915_active.h

@@ -70,4 +70,7 @@ 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_ */

drivers/gpu/drm/i915/i915_pci.c

@@ -26,6 +26,7 @@
 #include <linux/vgaarb.h>
 #include <linux/vga_switcheroo.h>
 
+#include "i915_active.h"
 #include "i915_drv.h"
 #include "i915_selftest.h"
 
@@ -798,6 +799,8 @@ 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;
@@ -829,6 +832,7 @@ static void __exit i915_exit(void)
 		return;
 
 	pci_unregister_driver(&i915_pci_driver);
+	i915_global_active_exit();
 }
 
 module_init(i915_init);