Tools

Splint

A good start, hasn't been maintained in at least 6 months, maybe longer. Outstanding bugs. Also looks like its a lot of effort.

XTC

Perhaps useful for refactoring the entire project, if we knew what we wanted to add.

Cscope

Helpful for figuring out everything that's going on.

Cscope is very helpful for tracking down where a function is used.
You can't do this from within VIM, however. The trick is to run
Cscope from the command line, to perform your search, and then to
hit '>' to save the results.

Next, I decided to track down some kernel memory.

Calls to kmalloc()

As it turns out, there are only 19 calls to kmalloc in the entire program.

File	Function	Line	Code
lib/nswap_hashtable.c	<global>	36	htable_t ht = (htable_t)kmalloc(sizeof(htable_t), GFP_NSWAP);
lib/nswap_hashtable.c	<global>	40	ht->table=(ht_list_t**)kmalloc(sizeof(ht_list_t*)*num_buckets,
lib/nswap_hashtable.c	<global>	49	rsv_ptr=kmalloc(sizeof(ht_list_t), GFP_NSWAP);
lib/nswap_threads.c	<global>	81	kmalloc(sizeof(nswap_thread_init_t), GFP_NSWAP);
lib/nswap_hashtable.c	get_from_reserves	15	l = (ht_list_t*)kmalloc(sizeof(ht_list_t), GFP_NSWAP);
lib/nswap_hashtable.c	ht_iter	198	cur=(ht_list_t*)kmalloc(sizeof(ht_list_t),
lib/nswap_net_io.c	nswap_tcp_alloc_socket	24	new_socket = kmalloc(sizeof(struct nswap_socket), GFP_NSWAP);
lib/nswap_net_io.c	nswap_udp_alloc_socket	56	new_socket = kmalloc(sizeof(struct nswap_socket), GFP_NSWAP);
lib/nswap_net_io.c	nswap_udp_alloc_socket	61	new_socket->addr = kmalloc(sizeof(struct sockaddr), GFP_NSWAP);
src/nswap_iptable.c	nswap_iptable_init	185	nswap_iptable = kmalloc(sizeof(struct nswap_ipentry)*NSWAP_MAXHOSTS,
src/nswapc_main.c	nswapc_init	292	io_request_sem = kmalloc(sizeof(struct semaphore), GFP_NSWAP);
src/nswapc_main.c	nswapc_init	319	worker_args = kmalloc(sizeof(struct worker_thread_args),
src/nswapd_mem.c	nswapd_mem_store	91	new_page = kmalloc(sizeof(page_data_t),(GFP_NSWAP));
src/nswapd_mem_mon.c	nswapd_mem_monitor_init	91	recent_monitor = kmalloc(sizeof(struct nswap_monitor_data), GFP_NSWAP);
src/nswapd_mem_mon.c	nswapd_mem_monitor_init	92	previous_monitor = kmalloc(sizeof(struct nswap_monitor_data), GFP_NSWAP);
src/nswapd_mem_mon_orig.c	nswapd_mem_monitor_init	91	recent_monitor = kmalloc(sizeof(struct nswap_monitor_data), GFP_NSWAP);
src/nswapd_mem_mon_orig.c	nswapd_mem_monitor_init	92	previous_monitor = kmalloc(sizeof(struct nswap_monitor_data), GFP_NSWAP);
src/nswapd_mem_monitor.c	nswapd_mem_monitor_init	93	recent_monitor = kmalloc(sizeof(struct nswap_monitor_data), GFP_NSWAP);
src/nswapd_mem_monitor.c	nswapd_mem_monitor_init	94	previous_monitor = kmalloc(sizeof(struct nswap_monitor_data), GFP_NSWAP);

There are 22 calls to kfree.

File	Function	Line	Code
lib/nswap_hashtable.c	ht_destroy	62	kfree(ht->table);
lib/nswap_hashtable.c	ht_destroy	66	kfree(rsv_ptr);
lib/nswap_hashtable.c	ht_destroy	69	kfree(ht);
lib/nswap_net_io.c	nswap_tcp_alloc_socket	34	kfree(new_socket);
lib/nswap_net_io.c	nswap_udp_alloc_socket	73	kfree(new_socket);
lib/nswap_net_io.c	nswap_tcp_close_socket	88	kfree(sock);
lib/nswap_net_io.c	nswap_udp_close_socket	99	kfree(sock->addr);
lib/nswap_net_io.c	nswap_udp_close_socket	101	kfree(sock);
lib/nswap_threads.c	nswap_thread_wrapper	47	kfree(args);
src/nswap_iptable.c	nswap_iptable_cleanup	728	kfree(nswap_iptable);
src/nswapc_main.c	request_worker_thr	448	kfree(worker_args);
src/nswapc_main.c	nswapc_cleanup	1472	kfree(io_request_sem);
src/nswapd_mem.c	nswapd_page_unmap_and_unwire	235	kfree(old);
src/nswapd_mem.c	nswapd_mem_release	271	kfree(old);
src/nswapd_mem.c	nswapd_mem_cleanup	470	kfree(htlist->info);
src/nswapd_mem.c	nswapd_mem_cleanup	471	kfree(htlist);
src/nswapd_mem_mon.c	nswapd_mem_monitor_cleanup	104	kfree(recent_monitor);
src/nswapd_mem_mon.c	nswapd_mem_monitor_cleanup	105	kfree(previous_monitor);
src/nswapd_mem_mon_orig.c	nswapd_mem_monitor_cleanup	104	kfree(recent_monitor);
src/nswapd_mem_mon_orig.c	nswapd_mem_monitor_cleanup	105	kfree(previous_monitor);
src/nswapd_mem_monitor.c	nswapd_mem_monitor_cleanup	106	kfree(recent_monitor);
src/nswapd_mem_monitor.c	nswapd_mem_monitor_cleanup	107	kfree(previous_monitor);

Pass 1

ht_iter() only gets called once, in src/nswapd_mem.c:nswapd_mem_cleanup where its results are immediately deleted.

Likewise, nswapd_mem_monitor_init() is only called once in src/nswapd_mem.c:nswapd_mem_init() and its results are freed in the corresponding call nswapd_mem_cleanup()

That leaves us with 12 kmallocs:

File	Function	Line	Code
lib/nswap_hashtable.c	<global>	36	htable_t ht = (htable_t)kmalloc(sizeof(htable_t), GFP_NSWAP);
lib/nswap_hashtable.c	<global>	40	ht->table=(ht_list_t**)kmalloc(sizeof(ht_list_t*)*num_buckets,
lib/nswap_hashtable.c	<global>	49	rsv_ptr=kmalloc(sizeof(ht_list_t), GFP_NSWAP);
lib/nswap_threads.c	<global>	81	kmalloc(sizeof(nswap_thread_init_t), GFP_NSWAP);
lib/nswap_hashtable.c	get_from_reserves	15	l = (ht_list_t*)kmalloc(sizeof(ht_list_t), GFP_NSWAP);
lib/nswap_net_io.c	nswap_tcp_alloc_socket	24	new_socket = kmalloc(sizeof(struct nswap_socket), GFP_NSWAP);
lib/nswap_net_io.c	nswap_udp_alloc_socket	56	new_socket = kmalloc(sizeof(struct nswap_socket), GFP_NSWAP);
lib/nswap_net_io.c	nswap_udp_alloc_socket	61	new_socket->addr = kmalloc(sizeof(struct sockaddr), GFP_NSWAP);
src/nswap_iptable.c	nswap_iptable_init	185	nswap_iptable = kmalloc(sizeof(struct nswap_ipentry)*NSWAP_MAXHOSTS,
src/nswapc_main.c	nswapc_init	292	io_request_sem = kmalloc(sizeof(struct semaphore), GFP_NSWAP);
src/nswapc_main.c	nswapc_init	319	worker_args = kmalloc(sizeof(struct worker_thread_args),
src/nswapd_mem.c	nswapd_mem_store	91	new_page = kmalloc(sizeof(page_data_t),(GFP_NSWAP));

and 14 kfrees.

File	Function	Line	Code
lib/nswap_hashtable.c	ht_destroy	62	kfree(ht->table);
lib/nswap_hashtable.c	ht_destroy	66	kfree(rsv_ptr);
lib/nswap_hashtable.c	ht_destroy	69	kfree(ht);
lib/nswap_net_io.c	nswap_tcp_alloc_socket	34	kfree(new_socket);
lib/nswap_net_io.c	nswap_udp_alloc_socket	73	kfree(new_socket);
lib/nswap_net_io.c	nswap_tcp_close_socket	88	kfree(sock);
lib/nswap_net_io.c	nswap_udp_close_socket	99	kfree(sock->addr);
lib/nswap_net_io.c	nswap_udp_close_socket	101	kfree(sock);
lib/nswap_threads.c	nswap_thread_wrapper	47	kfree(args);
src/nswap_iptable.c	nswap_iptable_cleanup	728	kfree(nswap_iptable);
src/nswapc_main.c	request_worker_thr	448	kfree(worker_args);
src/nswapc_main.c	nswapc_cleanup	1472	kfree(io_request_sem);
src/nswapd_mem.c	nswapd_page_unmap_and_unwire	235	kfree(old);
src/nswapd_mem.c	nswapd_mem_release	271	kfree(old);

Pass 2

lib/nswap_hashtable.c:get_from_reserves() is only called once in lib/nswap_hashtable.c:ht_insert().

ht_insert() allocates the list element itself. This element is not freed in ht_remove() because ht_remove uses add_to_reserves() to return the newly empty list element to a pool of empty list elements.

The memory is actually freed in ht_destroy().

ht_reset() simply moves all the allocated list elements into the reserved pool.

Now memory that gets sent into the reserved pool will never be freed during the course of the program. However, it does look to me like the hashtable library is clean.

That leaves us with 8 kmallocs:

File	Function	Line	Code
lib/nswap_threads.c	nswap_thread	81	kmalloc(sizeof(nswap_thread_init_t), GFP_NSWAP);
lib/nswap_net_io.c	nswap_tcp_alloc_socket	24	new_socket = kmalloc(sizeof(struct nswap_socket), GFP_NSWAP);
lib/nswap_net_io.c	nswap_udp_alloc_socket	56	new_socket = kmalloc(sizeof(struct nswap_socket), GFP_NSWAP);
lib/nswap_net_io.c	nswap_udp_alloc_socket	61	new_socket->addr = kmalloc(sizeof(struct sockaddr), GFP_NSWAP);
src/nswap_iptable.c	nswap_iptable_init	185	nswap_iptable = kmalloc(sizeof(struct nswap_ipentry)*NSWAP_MAXHOSTS,
src/nswapc_main.c	nswapc_init	292	io_request_sem = kmalloc(sizeof(struct semaphore), GFP_NSWAP);
src/nswapc_main.c	nswapc_init	319	worker_args = kmalloc(sizeof(struct worker_thread_args),
src/nswapd_mem.c	nswapd_mem_store	91	new_page = kmalloc(sizeof(page_data_t),(GFP_NSWAP));

and 13 kfrees.

File	Function	Line	Code
lib/nswap_net_io.c	nswap_tcp_alloc_socket	34	kfree(new_socket);
lib/nswap_net_io.c	nswap_udp_alloc_socket	73	kfree(new_socket);
lib/nswap_net_io.c	nswap_tcp_close_socket	88	kfree(sock);
lib/nswap_net_io.c	nswap_udp_close_socket	99	kfree(sock->addr);
lib/nswap_net_io.c	nswap_udp_close_socket	101	kfree(sock);
lib/nswap_threads.c	nswap_thread_wrapper	47	kfree(args);
src/nswap_iptable.c	nswap_iptable_cleanup	728	kfree(nswap_iptable);
src/nswapc_main.c	request_worker_thr	448	kfree(worker_args);
src/nswapc_main.c	nswapc_cleanup	1472	kfree(io_request_sem);
src/nswapd_mem.c	nswapd_page_unmap_and_unwire	235	kfree(old);
src/nswapd_mem.c	nswapd_mem_release	271	kfree(old);

Pass 3