intel: Add an interface to limit vma caching

There is a per-process limit on the number of vma that the process can
keep open, so we cannot keep an unlimited cache of unused vma's (besides
keeping track of all those vma in the kernel adds considerable overhead).
However, in order to work around inefficiencies in the kernel it is
beneficial to reuse the vma, so keep a MRU cache of vma.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

2 files changed, 99 insertions, 21 deletions

diff --git a/intel/intel_bufmgr.h b/intel/intel_bufmgr.h
index abe9711b..808e5dfa 100644
--- a/intel/intel_bufmgr.h
+++ b/intel/intel_bufmgr.h
@@ -145,6 +145,8 @@ drm_intel_bo *drm_intel_bo_gem_create_from_name(drm_intel_bufmgr *bufmgr,
 						unsigned int handle);
 void drm_intel_bufmgr_gem_enable_reuse(drm_intel_bufmgr *bufmgr);
 void drm_intel_bufmgr_gem_enable_fenced_relocs(drm_intel_bufmgr *bufmgr);
+void drm_intel_bufmgr_gem_set_vma_cache_size(drm_intel_bufmgr *bufmgr,
+					     int limit);
 int drm_intel_gem_bo_map_gtt(drm_intel_bo *bo);
 int drm_intel_gem_bo_unmap_gtt(drm_intel_bo *bo);
 int drm_intel_gem_bo_get_reloc_count(drm_intel_bo *bo);
diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
index db1416a6..c535dee6 100644
--- a/intel/intel_bufmgr_gem.c
+++ b/intel/intel_bufmgr_gem.c
@@ -97,6 +97,8 @@ typedef struct _drm_intel_bufmgr_gem {
 	time_t time;
 
 	drmMMListHead named;
+	drmMMListHead vma_cache;
+	int vma_count, vma_max;
 
 	uint64_t gtt_size;
 	int available_fences;
@@ -157,6 +159,7 @@ struct _drm_intel_bo_gem {
 	/** GTT virtual address for the buffer, saved across map/unmap cycles */
 	void *gtt_virtual;
 	int map_count;
+	drmMMListHead vma_list;
 
 	/** BO cache list */
 	drmMMListHead head;
@@ -701,6 +704,7 @@ retry:
 		}
 
 		DRMINITLISTHEAD(&bo_gem->name_list);
+		DRMINITLISTHEAD(&bo_gem->vma_list);
 	}
 
 	bo_gem->name = name;
@@ -866,6 +870,7 @@ drm_intel_bo_gem_create_from_name(drm_intel_bufmgr *bufmgr,
 	/* XXX stride is unknown */
 	drm_intel_bo_gem_set_in_aperture_size(bufmgr_gem, bo_gem);
 
+	DRMINITLISTHEAD(&bo_gem->vma_list);
 	DRMLISTADDTAIL(&bo_gem->name_list, &bufmgr_gem->named);
 	DBG("bo_create_from_handle: %d (%s)\n", handle, bo_gem->name);
 
@@ -880,6 +885,16 @@ drm_intel_gem_bo_free(drm_intel_bo *bo)
 	struct drm_gem_close close;
 	int ret;
 
+	DRMLISTDEL(&bo_gem->vma_list);
+	if (bo_gem->mem_virtual) {
+		munmap(bo_gem->mem_virtual, bo_gem->bo.size);
+		bufmgr_gem->vma_count--;
+	}
+	if (bo_gem->gtt_virtual) {
+		munmap(bo_gem->gtt_virtual, bo_gem->bo.size);
+		bufmgr_gem->vma_count--;
+	}
+
 	/* Close this object */
 	memset(&close, 0, sizeof(close));
 	close.handle = bo_gem->gem_handle;
@@ -921,6 +936,57 @@ drm_intel_gem_cleanup_bo_cache(drm_intel_bufmgr_gem *bufmgr_gem, time_t time)
 	bufmgr_gem->time = time;
 }
 
+static void drm_intel_gem_bo_purge_vma_cache(drm_intel_bufmgr_gem *bufmgr_gem)
+{
+	DBG("%s: count=%d, limit=%d\n", __FUNCTION__,
+	    bufmgr_gem->vma_count, bufmgr_gem->vma_max);
+
+	if (bufmgr_gem->vma_max < 0)
+		return;
+
+	while (bufmgr_gem->vma_count > bufmgr_gem->vma_max) {
+		drm_intel_bo_gem *bo_gem;
+
+		bo_gem = DRMLISTENTRY(drm_intel_bo_gem,
+				      bufmgr_gem->vma_cache.next,
+				      vma_list);
+		assert(bo_gem->map_count == 0);
+		DRMLISTDEL(&bo_gem->vma_list);
+
+		if (bo_gem->mem_virtual) {
+			munmap(bo_gem->mem_virtual, bo_gem->bo.size);
+			bo_gem->mem_virtual = NULL;
+			bufmgr_gem->vma_count--;
+		}
+		if (bo_gem->gtt_virtual) {
+			munmap(bo_gem->gtt_virtual, bo_gem->bo.size);
+			bo_gem->gtt_virtual = NULL;
+			bufmgr_gem->vma_count--;
+		}
+	}
+}
+
+static void drm_intel_gem_bo_add_to_vma_cache(drm_intel_bufmgr_gem *bufmgr_gem,
+					      drm_intel_bo_gem *bo_gem)
+{
+	DRMLISTADDTAIL(&bo_gem->vma_list, &bufmgr_gem->vma_cache);
+	if (bo_gem->mem_virtual)
+		bufmgr_gem->vma_count++;
+	if (bo_gem->gtt_virtual)
+		bufmgr_gem->vma_count++;
+	drm_intel_gem_bo_purge_vma_cache(bufmgr_gem);
+}
+
+static void drm_intel_gem_bo_remove_from_vma_cache(drm_intel_bufmgr_gem *bufmgr_gem,
+						   drm_intel_bo_gem *bo_gem)
+{
+	DRMLISTDEL(&bo_gem->vma_list);
+	if (bo_gem->mem_virtual)
+		bufmgr_gem->vma_count--;
+	if (bo_gem->gtt_virtual)
+		bufmgr_gem->vma_count--;
+}
+
 static void
 drm_intel_gem_bo_unreference_final(drm_intel_bo *bo, time_t time)
 {
@@ -958,14 +1024,6 @@ drm_intel_gem_bo_unreference_final(drm_intel_bo *bo, time_t time)
 		DBG("bo freed with non-zero map-count %d\n", bo_gem->map_count);
 		bo_gem->map_count = 0;
 	}
-	if (bo_gem->mem_virtual) {
-		munmap(bo_gem->mem_virtual, bo_gem->bo.size);
-		bo_gem->mem_virtual = 0;
-	}
-	if (bo_gem->gtt_virtual) {
-		munmap(bo_gem->gtt_virtual, bo_gem->bo.size);
-		bo_gem->gtt_virtual = 0;
-	}
 
 	DRMLISTDEL(&bo_gem->name_list);
 
@@ -979,6 +1037,9 @@ drm_intel_gem_bo_unreference_final(drm_intel_bo *bo, time_t time)
 		bo_gem->name = NULL;
 		bo_gem->validate_index = -1;
 
+		if (bo_gem->mem_virtual || bo_gem->gtt_virtual)
+			drm_intel_gem_bo_add_to_vma_cache(bufmgr_gem, bo_gem);
+
 		DRMLISTADDTAIL(&bo_gem->head, &bucket->head);
 	} else {
 		drm_intel_gem_bo_free(bo);
@@ -1023,11 +1084,14 @@ static int drm_intel_gem_bo_map(drm_intel_bo *bo, int write_enable)
 
 	pthread_mutex_lock(&bufmgr_gem->lock);
 
+	if (bo_gem->map_count++ == 0)
+		drm_intel_gem_bo_remove_from_vma_cache(bufmgr_gem, bo_gem);
+
 	if (!bo_gem->mem_virtual) {
 		struct drm_i915_gem_mmap mmap_arg;
 
 		DBG("bo_map: %d (%s)\n", bo_gem->gem_handle, bo_gem->name);
-		assert(bo_gem->map_count == 0);
+		assert(bo_gem->map_count == 1);
 
 		memset(&mmap_arg, 0, sizeof(mmap_arg));
 		mmap_arg.handle = bo_gem->gem_handle;
@@ -1041,6 +1105,8 @@ static int drm_intel_gem_bo_map(drm_intel_bo *bo, int write_enable)
 			DBG("%s:%d: Error mapping buffer %d (%s): %s .\n",
 			    __FILE__, __LINE__, bo_gem->gem_handle,
 			    bo_gem->name, strerror(errno));
+			if (--bo_gem->map_count == 0)
+				drm_intel_gem_bo_add_to_vma_cache(bufmgr_gem, bo_gem);
 			pthread_mutex_unlock(&bufmgr_gem->lock);
 			return ret;
 		}
@@ -1049,7 +1115,6 @@ static int drm_intel_gem_bo_map(drm_intel_bo *bo, int write_enable)
 	DBG("bo_map: %d (%s) -> %p\n", bo_gem->gem_handle, bo_gem->name,
 	    bo_gem->mem_virtual);
 	bo->virtual = bo_gem->mem_virtual;
-	bo_gem->map_count++;
 
 	set_domain.handle = bo_gem->gem_handle;
 	set_domain.read_domains = I915_GEM_DOMAIN_CPU;
@@ -1083,13 +1148,16 @@ int drm_intel_gem_bo_map_gtt(drm_intel_bo *bo)
 
 	pthread_mutex_lock(&bufmgr_gem->lock);
 
+	if (bo_gem->map_count++ == 0)
+		drm_intel_gem_bo_remove_from_vma_cache(bufmgr_gem, bo_gem);
+
 	/* Get a mapping of the buffer if we haven't before. */
 	if (bo_gem->gtt_virtual == NULL) {
 		struct drm_i915_gem_mmap_gtt mmap_arg;
 
 		DBG("bo_map_gtt: mmap %d (%s)\n", bo_gem->gem_handle,
 		    bo_gem->name);
-		assert(bo_gem->map_count == 0);
+		assert(bo_gem->map_count == 1);
 
 		memset(&mmap_arg, 0, sizeof(mmap_arg));
 		mmap_arg.handle = bo_gem->gem_handle;
@@ -1119,13 +1187,14 @@ int drm_intel_gem_bo_map_gtt(drm_intel_bo *bo)
 			    __FILE__, __LINE__,
 			    bo_gem->gem_handle, bo_gem->name,
 			    strerror(errno));
+			if (--bo_gem->map_count == 0)
+				drm_intel_gem_bo_add_to_vma_cache(bufmgr_gem, bo_gem);
 			pthread_mutex_unlock(&bufmgr_gem->lock);
 			return ret;
 		}
 	}
 
 	bo->virtual = bo_gem->gtt_virtual;
-	bo_gem->map_count++;
 
 	DBG("bo_map_gtt: %d (%s) -> %p\n", bo_gem->gem_handle, bo_gem->name,
 	    bo_gem->gtt_virtual);
@@ -1160,6 +1229,8 @@ static int drm_intel_gem_bo_unmap(drm_intel_bo *bo)
 
 	pthread_mutex_lock(&bufmgr_gem->lock);
 
+	assert(bo_gem->map_count > 0);
+
 	if (bo_gem->mapped_cpu_write) {
 		/* Cause a flush to happen if the buffer's pinned for
 		 * scanout, so the results show up in a timely manner.
@@ -1180,15 +1251,7 @@ static int drm_intel_gem_bo_unmap(drm_intel_bo *bo)
 	 * limits and cause later failures.
 	 */
 	if (--bo_gem->map_count == 0) {
-		if (bo_gem->mem_virtual) {
-			munmap(bo_gem->mem_virtual, bo_gem->bo.size);
-			bo_gem->mem_virtual = NULL;
-		}
-		if (bo_gem->gtt_virtual) {
-			munmap(bo_gem->gtt_virtual, bo_gem->bo.size);
-			bo_gem->gtt_virtual = NULL;
-		}
-
+		drm_intel_gem_bo_add_to_vma_cache(bufmgr_gem, bo_gem);
 		bo->virtual = NULL;
 	}
 	pthread_mutex_unlock(&bufmgr_gem->lock);
@@ -2174,6 +2237,16 @@ init_cache_buckets(drm_intel_bufmgr_gem *bufmgr_gem)
 	}
 }
 
+void
+drm_intel_bufmgr_gem_set_vma_cache_size(drm_intel_bufmgr *bufmgr, int limit)
+{
+	drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bufmgr;
+
+	bufmgr_gem->vma_max = limit;
+
+	drm_intel_gem_bo_purge_vma_cache(bufmgr_gem);
+}
+
 /**
  * Initializes the GEM buffer manager, which uses the kernel to allocate, map,
  * and manage map buffer objections.
@@ -2333,5 +2406,8 @@ drm_intel_bufmgr_gem_init(int fd, int batch_size)
 	DRMINITLISTHEAD(&bufmgr_gem->named);
 	init_cache_buckets(bufmgr_gem);
 
+	DRMINITLISTHEAD(&bufmgr_gem->vma_cache);
+	bufmgr_gem->vma_max = -1; /* unlimited by default */
+
 	return &bufmgr_gem->bufmgr;
 }