gpu: Be more aggressive about GC'ing dead textures

When we encounter many dead textures, we want to GC. Textures can take
up fds (potentially even more than 1) and when we are not collecting
them quickly enough, we may run out of fds.

So GC when more then 50 dead textures exist.

An example for this happening is recent Mesa with llvmpipe udmabuf
support, which takes 2 fds per texture and the test in
testsuite/gdk/memorytexture that creates 800 textures of ~1 pixel each,
which it diligently releases but doesn't GC.

Related: #6917

gsk/gpu/gskgpucache.c

@@ -48,6 +48,7 @@ struct _GskGpuCache
 
   GskGpuCachedAtlas *current_atlas;
 
+  /* atomic */ gsize dead_textures;
   /* atomic */ gsize dead_texture_pixels;
 };
 
@@ -372,6 +373,7 @@ struct _GskGpuCachedTexture
                                * weak ref.
                                */
 
+  gsize *dead_textures_counter;
   gsize *dead_pixels_counter;
 
   GdkTexture *texture;
@@ -470,7 +472,10 @@ gsk_gpu_cached_texture_destroy_cb (gpointer data)
   GskGpuCachedTexture *self = data;
 
   if (!gsk_gpu_cached_texture_is_invalid (self))
-    g_atomic_pointer_add (self->dead_pixels_counter, ((GskGpuCached *) self)->pixels);
+    {
+      g_atomic_pointer_add (self->dead_textures_counter, 1);
+      g_atomic_pointer_add (self->dead_pixels_counter, ((GskGpuCached *) self)->pixels);
+    }
 
   if (g_atomic_int_dec_and_test (&self->use_count))
     g_free (self);
@@ -508,6 +513,7 @@ gsk_gpu_cached_texture_new (GskGpuCache   *cache,
   self->image = g_object_ref (image);
   self->color_state = color_state;
   ((GskGpuCached *)self)->pixels = gsk_gpu_image_get_width (image) * gsk_gpu_image_get_height (image);
+  self->dead_textures_counter = &cache->dead_textures;
   self->dead_pixels_counter = &cache->dead_texture_pixels;
   self->use_count = 2;
 
@@ -537,6 +543,7 @@ struct _GskGpuCachedTile
                                * list) and by the texture (via weak ref)
                                */
 
+  gsize *dead_textures_counter;
   gsize *dead_pixels_counter;
 
   GskGpuImage *image;
@@ -609,7 +616,10 @@ gsk_gpu_cached_tile_destroy_cb (gpointer data)
   GskGpuCachedTile *self = data;
 
   if (!gsk_gpu_cached_tile_is_invalid (self))
-    g_atomic_pointer_add (self->dead_pixels_counter, ((GskGpuCached *) self)->pixels);
+    {
+      g_atomic_pointer_add (self->dead_textures_counter, 1);
+      g_atomic_pointer_add (self->dead_pixels_counter, ((GskGpuCached *) self)->pixels);
+    }
 
   if (g_atomic_int_dec_and_test (&self->use_count))
     g_free (self);
@@ -649,6 +659,7 @@ gsk_gpu_cached_tile_new (GskGpuCache   *cache,
   self->image = g_object_ref (image);
   self->color_state = gdk_color_state_ref (color_state);
   ((GskGpuCached *)self)->pixels = gsk_gpu_image_get_width (image) * gsk_gpu_image_get_height (image);
+  self->dead_textures_counter = &cache->dead_textures;
   self->dead_pixels_counter = &cache->dead_texture_pixels;
   self->use_count = 2;
 
@@ -894,6 +905,7 @@ gsk_gpu_cache_gc (GskGpuCache *self,
         is_empty &= cached->stale;
     }
 
+  g_atomic_pointer_set (&self->dead_textures, 0);
   g_atomic_pointer_set (&self->dead_texture_pixels, 0);
 
   if (GSK_DEBUG_CHECK (CACHE))
@@ -904,6 +916,12 @@ gsk_gpu_cache_gc (GskGpuCache *self,
   return is_empty;
 }
 
+gsize
+gsk_gpu_cache_get_dead_textures (GskGpuCache *self)
+{
+  return GPOINTER_TO_SIZE (g_atomic_pointer_get (&self->dead_textures));
+}
+
 gsize
 gsk_gpu_cache_get_dead_texture_pixels (GskGpuCache *self)
 {

gsk/gpu/gskgpucacheprivate.h

@@ -64,6 +64,7 @@ void                    gsk_gpu_cache_set_time                          (GskGpuC
 gboolean                gsk_gpu_cache_gc                                (GskGpuCache            *self,
                                                                          gint64                  cache_timeout,
                                                                          gint64                  timestamp);
+gsize                   gsk_gpu_cache_get_dead_textures                 (GskGpuCache            *self);
 gsize                   gsk_gpu_cache_get_dead_texture_pixels           (GskGpuCache            *self);
 GskGpuImage *           gsk_gpu_cache_get_atlas_image                   (GskGpuCache            *self);
 

gsk/gpu/gskgpudevice.c

@@ -80,7 +80,7 @@ void
 gsk_gpu_device_maybe_gc (GskGpuDevice *self)
 {
   GskGpuDevicePrivate *priv = gsk_gpu_device_get_instance_private (self);
-  gsize dead_texture_pixels;
+  gsize dead_texture_pixels, dead_textures;
 
   if (priv->cache_timeout < 0)
     return;
@@ -88,11 +88,13 @@ gsk_gpu_device_maybe_gc (GskGpuDevice *self)
   if (priv->cache == NULL)
     return;
 
+  dead_textures = gsk_gpu_cache_get_dead_textures (priv->cache);
   dead_texture_pixels = gsk_gpu_cache_get_dead_texture_pixels (priv->cache);
 
-  if (priv->cache_timeout == 0 || dead_texture_pixels > 1000000)
+  if (priv->cache_timeout == 0 || dead_textures > 50 || dead_texture_pixels > 1000 * 1000)
     {
-      GSK_DEBUG (CACHE, "Pre-frame GC (%" G_GSIZE_FORMAT " dead pixels)", dead_texture_pixels);
+      GSK_DEBUG (CACHE, "Pre-frame GC (%" G_GSIZE_FORMAT " dead textures, %" G_GSIZE_FORMAT " dead pixels)",
+                 dead_textures, dead_texture_pixels);
       gsk_gpu_device_gc (self, g_get_monotonic_time ());
     }
 }