Variables extern bool trimming_cycle; Determines if we are trimming - if we are nearly out of space static page_queue page_free_queue; The queue that holds unused (but not cleared) pages static page_queue page_clear_queue; The queue that holds cleared (0'ed) pages static page_queue page_modified_queue; The queue that holds altered pages static page_queue page_active_queue; The queue that holds in use pages that are not altered static vm_page *all_pages; Every page in the system static addr physical_page_offset; The first address of real ram static unsigned int num_pages; Total number of pages in the system static spinlock_t page_lock; A lock to protect the queues. static sem_id modified_pages_available; A semaphore to indicate if there are pages that need to be written to disk static void clear_page(addr pa); Sets all values in this page to 0. static vm_page * dequeue_page(page_queue *q) Standard queue remove first page; has count; no locking void dump_page_stats(int argc, char **argv); Dumps counts of each state (active, inactive, busy, not used, modified, free, cleared, wired) void dump_free_page_table(int argc, char **argv) Not done. static void enqueue_page(page_queue *q, vm_page *page) Standard queue add a page; has count; no locking; SPECIAL - for page_modified_queue, if there is only one page modified (new one), release semaphore static bool is_page_in_phys_range(kernel_args *ka, addr paddr) Determines if a physical address is in the physical memory that exists. static void move_page_to_queue(page_queue *from_q, page_queue *to_q, vm_page *page) Removes the page from the from_q and adds it to the to_q. static int pageout_daemon() aquires the "modified pages available" semaphore. Gets first page from modified list. Sets it to busy, updates all processes mapping this page that it is no longer a modified page, writes it out to disk, then puts it on the active list (i.e. not modified). Doesn't write out "anonymous" blocks unless we are trimming. static int page_scrubber(void *); Every 1/10 second, takes a page from the free queue, memsets it to 0's, then puts it on the clear queue. static void remove_page_from_queue(page_queue *q, vm_page *page) Removes a given page from the given page queue. No locking. addr vm_alloc_from_ka_struct(kernel_args *ka, unsigned int size, int lock) Gets virtual space in the ka using vm_alloc_vspace_from_ka_struct, then uses vm_alloc_ppage_from_kernel_struct to find a physical page to map it to. static addr vm_alloc_ppage_from_kernel_struct(kernel_args *ka) Attempts to extend, by one page, one of the phys_alloc_range blocks in the kernel args. static addr vm_alloc_vspace_from_ka_struct(kernel_args *ka, unsigned int size) Attempts to find an address range that can be extended to hold size bytes. vm_page * vm_lookup_page(addr page_num) Does the math to get vm_page pointer from a page number. int vm_mark_page_inuse(addr page) Calls vm_mark_page_range_inuse with len of 1. int vm_mark_page_range_inuse(addr start_page, addr len) Sets state to PAGE_STATE_UNUSED for all pages in this range. vm_page * vm_page_allocate_page(int page_state) Gets a single page from the clear or free queue (from page_state), fall back to the other. vm_page * vm_page_allocate_page_run(int page_state, addr len) Attempts to find a run of pages "len" long that are either free or clear. If found, pulls them from their queues and calls vm_page_set_state_nolock on them vm_page * vm_page_allocate_specific_page(addr page_num, int page_state) Finds this page, removes it from the clear or free queue, clears it if necessary and returns. Returns NULL for not found or page in use. int vm_page_init(kernel_args *ka) Initializes the free, clear, modified and active queues. Sets up the vm structures. int vm_page_init2(kernel_args *ka) Properly maps the vm structures allocated in vm_page_init. int vm_page_init_postthread(kernel_args *ka) Creates the page scrubber and the pageout daemon. addr vm_page_num_pages() Returns the total number of pages. addr vm_page_num_free_pages() Returns count of pages in free and clear queues. int vm_page_set_state(vm_page *page, int page_state) Locks, then calls vm_page_set_state_nolock, then unlocks. static int vm_page_set_state_nolock(vm_page *page, int page_state); Moves a page from the state that it is in to the state specified, and moves it from the old queue to the new one.