Change Futatabi frames to be cached as textures instead of in system memory.

[nageru] / futatabi / pbo_pool.h

diff --git a/futatabi/pbo_pool.h b/futatabi/pbo_pool.h
new file mode 100644 (file)
index 0000000..20c61e4
--- /dev/null
+++ b/futatabi/pbo_pool.h
@@ -0,0 +1,51 @@
+#ifndef _PBO_POOL_H
+#define _PBO_POOL_H 1
+
+// Keeps a pool of persistently mapped PBOs around that can be used as staging
+// buffers for texture uploads. (Uploading from a PBO is asynchronous and done
+// by the GPU, so assuming we don't need an extra copy into the PBO, this is a
+// significant win over uploading from regular malloc-ed RAM.)
+//
+// Unlike Nageru's PBOFrameAllocator, these are not connected to
+// a given frame, since we can have thousands of frames in the cache
+// at any given time. Thus, we need to have separate fences for each PBO
+// to know that the upload is done.
+
+#include <mutex>
+#include <queue>
+
+#include <epoxy/gl.h>
+
+#include "shared/ref_counted_gl_sync.h"
+
+struct PBO {
+       GLuint pbo;
+       uint8_t *ptr;  // Mapped memory.
+       RefCountedGLsync upload_done;
+};
+
+class PBOPool {
+public:
+       PBOPool(size_t pbo_size = 8 << 20,  // 8 MB, large enough for 1080p 4:2:2.
+                size_t num_pbos = 8,
+                GLenum buffer = GL_PIXEL_UNPACK_BUFFER_ARB,
+                GLenum permissions = GL_MAP_WRITE_BIT,
+                GLenum map_bits = GL_MAP_FLUSH_EXPLICIT_BIT);
+
+       PBO alloc_pbo();
+       void release_pbo(PBO pbo);  // Set a fence on upload_done if the PBO may still be in use.
+
+private:
+       PBO create_pbo();
+
+       std::mutex freelist_mutex;
+       std::queue<PBO> freelist;
+
+       size_t pbo_size;
+       GLenum buffer, permissions, map_bits;
+};
+
+extern PBOPool *global_pbo_pool;
+void init_pbo_pool();  // Idempotent.
+
+#endif  // !defined(_PBO_POOL_H)