This PR updates our Metal buffer tracking logic to use a NSHashTable to track alive buffers. NSHashTable is configured to hold weak references to the buffers we add to it. When a buffer is deallocated, it is automatically removed from the hash table. By counting the number of buffers in the hash table, we get an accurate count of the number of alive buffers.
The previous implementation had the limitation that once we pass a buffer off to Metal (when a command buffer becomes the sole owner of it, for example), we assume Metal will eventually release it and and decrement our count. In reality, that buffer could stay alive for a frame or two while the command buffer executes. Using the hash table should give us a more accurate tally of the alive buffer count.
This PR updates our Metal buffer tracking logic to use a
NSHashTableto track alive buffers.NSHashTableis configured to hold weak references to the buffers we add to it. When a buffer is deallocated, it is automatically removed from the hash table. By counting the number of buffers in the hash table, we get an accurate count of the number of alive buffers.The previous implementation had the limitation that once we pass a buffer off to Metal (when a command buffer becomes the sole owner of it, for example), we assume Metal will eventually release it and and decrement our count. In reality, that buffer could stay alive for a frame or two while the command buffer executes. Using the hash table should give us a more accurate tally of the alive buffer count.