From 1bac8b439abcf30a09c6dcbfa58d15beb6b261d9 Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Sun, 28 Jan 2024 10:45:59 -0500
Subject: [PATCH] gpu: Be more aggressive about cache gc

Count dead pixels in textures (ie the number of pixels in GPU
textures that are no longer backed by an alive GdkTexture object),
and when the there's too many, do a gc before rendering the next
frame.
---
 gsk/gpu/gskgpudevice.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/gsk/gpu/gskgpudevice.c b/gsk/gpu/gskgpudevice.c
index 6f22e7558c..c1af408f16 100644
--- a/gsk/gpu/gskgpudevice.c
+++ b/gsk/gpu/gskgpudevice.c
@@ -46,6 +46,8 @@ struct _GskGpuDevicePrivate
   GHashTable *glyph_cache;
 
   GskGpuCachedAtlas *current_atlas;
+
+  /* atomic */ gsize dead_texture_pixels;
 };
 
 G_DEFINE_TYPE_WITH_PRIVATE (GskGpuDevice, gsk_gpu_device, G_TYPE_OBJECT)
@@ -73,7 +75,7 @@ struct _GskGpuCached
 
   gint64 timestamp;
   gboolean stale;
-  guint pixels;   /* For glyphs, pixels. For atlases, dead pixels */
+  guint pixels;   /* For glyphs and textures, pixels. For atlases, dead pixels */
 };
 
 static inline void
@@ -245,6 +247,8 @@ struct _GskGpuCachedTexture
                                * weak ref.
                                */
 
+  gsize *dead_pixels_counter;
+
   GdkTexture *texture;
   GskGpuImage *image;
 };
@@ -304,16 +308,19 @@ static const GskGpuCachedClass GSK_GPU_CACHED_TEXTURE_CLASS =
   gsk_gpu_cached_texture_should_collect
 };
 
+/* Note: this function can run in an arbitrary thread, so it can
+ * only access things atomically
+ */
 static void
 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);
+
   if (g_atomic_int_dec_and_test (&self->use_count))
-    {
-      g_free (self);
-      return;
-    }
+    g_free (self);
 }
 
 static GskGpuCachedTexture *
@@ -336,6 +343,8 @@ gsk_gpu_cached_texture_new (GskGpuDevice *device,
   self = gsk_gpu_cached_new (device, &GSK_GPU_CACHED_TEXTURE_CLASS, NULL);
   self->texture = texture;
   self->image = g_object_ref (image);
+  ((GskGpuCached *)self)->pixels = gsk_gpu_image_get_width (image) * gsk_gpu_image_get_height (image);
+  self->dead_pixels_counter = &priv->dead_texture_pixels;
   self->use_count = 2;
 
   if (!gdk_texture_set_render_data (texture, device, self, gsk_gpu_cached_texture_destroy_cb))
@@ -497,6 +506,8 @@ gsk_gpu_device_gc (GskGpuDevice *self,
         gsk_gpu_cached_free (self, cached);
     }
 
+  g_atomic_pointer_set (&priv->dead_texture_pixels, 0);
+
   if (GSK_DEBUG_CHECK (GLYPH_CACHE))
     print_cache_stats (self);
 
@@ -522,15 +533,22 @@ void
 gsk_gpu_device_maybe_gc (GskGpuDevice *self)
 {
   GskGpuDevicePrivate *priv = gsk_gpu_device_get_instance_private (self);
+  gsize dead_texture_pixels;
 
   if (priv->cache_timeout < 0)
     return;
 
-  if (priv->cache_timeout == 0)
+  dead_texture_pixels = GPOINTER_TO_SIZE (g_atomic_pointer_get (&priv->dead_texture_pixels));
+
+  if (priv->cache_timeout == 0 || dead_texture_pixels > 1000000)
     {
-      GSK_DEBUG (GLYPH_CACHE, "Pre-frame GC");
+      GSK_DEBUG (GLYPH_CACHE, "Pre-frame GC (%lu dead pixels)", dead_texture_pixels);
       gsk_gpu_device_gc (self, g_get_monotonic_time ());
     }
+  else
+    {
+      GSK_DEBUG (GLYPH_CACHE, "No pre-frame GC (%lu dead pixels)", dead_texture_pixels);
+    }
 }
 
 void