eightbitraptor[wiki]

Ruby Heaps

There are two heaps. the eden heap and the tomb heap. Each heap consists of pages (see [ruby-heap-pages]) each page holds [rvalue] objects.

    rb_heap_t tomb_heap; /* heap for zombies and ghosts */

wtf is the tomb heap for, what is a zombie and what is a ghost?

Ruby allocates objects on the eden heap, until that heap is full. When GC cleans up all the objects on a heap page, that page gets moved to the tomb heap. When Ruby runs out of pages on the eden heap it will check to see if there are any pages on the tomb heap that can be resurrected before asking the operating system to malloc enough memory for another page to extend the eden heap (TODO: More detail here about tomb heaps)

• rb_heap_t a struct to hold pages of RVALUE objects

• free_pages - this is a pointer to a heap_page. heap pages have a free_next pointer that turns heap pages into a singly linked list. A page is defined as free when it has at least one slot that is free.

• using_page - this is also a pointer to a heap_page. When

• pages - this is a list_head. Not sure what that is or what this is for

• sweeping_page - this is a pointer to a heap_page, the inline comment tells me that it’s an “iterator for .pages”, not sure what this means yet.

• total_pages - ?

• total_slots - ? (how many slots fit in a page)