vulkan: Don't create more than one render object

By creating unlimited render objects, we would never wait on the GPU.

This would mean that if the GPU was the bottleneck, we would fill its
queue with render commands faster than it could process them.

And because the nvidia binary driver and my code work surprisingly well
and bugfree, this lead to exhaustion of RAM. I had 50GB of swap
configured and my hard disk was quicker as swap storage than my GPU was
at processing the commands, so stuff still filled up.

At that point my computer became rather unresponsive and I decided to
reboot it, so I that could write this patch.

1 files changed, 4 insertions, 20 deletions

diff --git a/gsk/gskvulkanrenderer.c b/gsk/gskvulkanrenderer.c
index 488b8f4dd7..2f71dc0066 100644
--- a/gsk/gskvulkanrenderer.c
+++ b/gsk/gskvulkanrenderer.c
@@ -33,7 +33,7 @@ struct _GskVulkanRenderer
 
   VkSampler sampler;
 
-  GSList *renders;
+  GskVulkanRender *render;
 
 #ifdef G_ENABLE_DEBUG
   ProfileTimers profile_timers;
@@ -123,8 +123,7 @@ gsk_vulkan_renderer_realize (GskRenderer  *renderer,
                     self);
   gsk_vulkan_renderer_update_images_cb (self->vulkan, self);
 
-  /* We will need at least one render object, so create it early where we can still fail fine */
-  self->renders = g_slist_prepend (self->renders, gsk_vulkan_render_new (renderer, self->vulkan));
+  self->render = gsk_vulkan_render_new (renderer, self->vulkan);
 
   return TRUE;
 }
@@ -135,8 +134,7 @@ gsk_vulkan_renderer_unrealize (GskRenderer *renderer)
   GskVulkanRenderer *self = GSK_VULKAN_RENDERER (renderer);
   VkDevice device;
 
-  g_slist_free_full (self->renders, (GDestroyNotify) gsk_vulkan_render_free);
-  self->renders = NULL;
+  g_clear_pointer (&self->render, gsk_vulkan_render_free);
 
   device = gdk_vulkan_context_get_device (self->vulkan);
 
@@ -159,7 +157,6 @@ gsk_vulkan_renderer_render (GskRenderer   *renderer,
 {
   GskVulkanRenderer *self = GSK_VULKAN_RENDERER (renderer);
   GskVulkanRender *render;
-  GSList *l;
 #ifdef G_ENABLE_DEBUG
   GskProfiler *profiler;
   gint64 cpu_time;
@@ -170,20 +167,7 @@ gsk_vulkan_renderer_render (GskRenderer   *renderer,
   gsk_profiler_timer_begin (profiler, self->profile_timers.cpu_time);
 #endif
 
-  for (l = self->renders; l; l = l->next)
-    {
-      if (!gsk_vulkan_render_is_busy (l->data))
-        break;
-    }
-  if (l)
-    {
-      render = l->data;
-    }
-  else
-    {
-      render = gsk_vulkan_render_new (renderer, self->vulkan);
-      self->renders = g_slist_prepend (self->renders, render);
-    }
+  render = self->render;
 
   gsk_vulkan_render_reset (render, self->targets[gdk_vulkan_context_get_draw_index (self->vulkan)]);