linuxcompressed-checkins

[Rodrigo S. de C. <rc...@us...>]

Update of /cvsroot/linuxcompressed/linux/mm/comp_cache
In directory usw-pr-cvs1:/tmp/cvs-serv25332/mm/comp_cache

Modified Files:
	aux.c main.c swapin.c swapout.c 
Log Message:
Some changes regarding code optimization. These modifications have improved
a lot some tests (fillmem) we performed to test our current code.

- hash function changed to be arch-independent (by using SWP_OFFSET) and
also has been improved (shifting one position to the left).

- hash table size is in function of COMP_CACHE_CACHE_SIZE. It was set to a
static value and that hurts performance pretty badly for bigger sizes of
compressed cache. This change breaks the kernel parameter compsize=, but I
don't know if it's worth to add a variable to hold the hash table size since
the macro that uses this value (fragment_hashfn) is called many times.

- now the option in kernel config menu warns about the need of having a
maximum size of compressed cache as a power of two number for this hash
table size. If it's not a power of two, it breaks the hash function and the
performance drops heavily. To solve this problem, we could add a variable
that would be set to a reasonable value (a power of two) and in function of
the maximum size of the compressed cache, but there's the problem explained
above.

- swap_out_fragments() never sleeps to lock a page. If it couldn't be locked
at once, move it to the end of the LRU list and tries to lock the next.

- removed checksum from the comp_cache_fragment_t and checksum computation
from get_comp_cache_page() and decompress_page(). It added a huge overhead
in our tests.



Index: aux.c
===================================================================
RCS file: /cvsroot/linuxcompressed/linux/mm/comp_cache/aux.c,v
retrieving revision 1.8
retrieving revision 1.9
diff -C2 -r1.8 -r1.9
*** aux.c	2001/12/20 13:24:32	1.8
--- aux.c	2002/01/04 22:24:07	1.9
***************
*** 2,6 ****
   * linux/mm/comp_cache/aux.c
   *
!  * Time-stamp: <2001-12-20 10:33:21 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
--- 2,6 ----
   * linux/mm/comp_cache/aux.c
   *
!  * Time-stamp: <2002-01-04 19:10:26 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
***************
*** 14,18 ****
  #include <linux/init.h>
  
! comp_cache_fragment_t * fragment_hash[HTABLE_SIZE];
  
  /* computes (unsigned long long x) / (unsigned long long y) */
--- 14,18 ----
  #include <linux/init.h>
  
! comp_cache_fragment_t * fragment_hash[FRAGMENT_HASH_SIZE];
  
  /* computes (unsigned long long x) / (unsigned long long y) */
***************
*** 62,67 ****
  add_fragment_to_hash_table(comp_cache_fragment_t * new_fragment) {
  	comp_cache_fragment_t ** fragment;
  	
! 	fragment = &fragment_hash[hashfn(new_fragment->index)];
  
  	if ((new_fragment->next_hash = *fragment))
--- 62,70 ----
  add_fragment_to_hash_table(comp_cache_fragment_t * new_fragment) {
  	comp_cache_fragment_t ** fragment;
+ 	swp_entry_t entry;
+ 
+ 	entry = (swp_entry_t) { new_fragment->index };
  	
! 	fragment = &fragment_hash[fragment_hashfn(entry)];
  
  	if ((new_fragment->next_hash = *fragment))
***************
*** 120,124 ****
  	*fragment_out = NULL;
  
! 	for (fragment = fragment_hash[hashfn(entry.val)]; fragment != NULL; fragment = fragment->next_hash) {
  		if (fragment->index == entry.val && !CompFragmentFreed(fragment)) {
  			*fragment_out = fragment;
--- 123,127 ----
  	*fragment_out = NULL;
  
! 	for (fragment = fragment_hash[fragment_hashfn(entry)]; fragment != NULL; fragment = fragment->next_hash) {
  		if (fragment->index == entry.val && !CompFragmentFreed(fragment)) {
  			*fragment_out = fragment;
***************
*** 372,376 ****
  	
  	/* inits fragment hash table */
! 	for (i = 0; i < HTABLE_SIZE; i++)
  		fragment_hash[i] = NULL;
  }
--- 375,379 ----
  	
  	/* inits fragment hash table */
! 	for (i = 0; i < FRAGMENT_HASH_SIZE; i++)
  		fragment_hash[i] = NULL;
  }

Index: main.c
===================================================================
RCS file: /cvsroot/linuxcompressed/linux/mm/comp_cache/main.c,v
retrieving revision 1.14
retrieving revision 1.15
diff -C2 -r1.14 -r1.15
*** main.c	2002/01/02 16:59:05	1.14
--- main.c	2002/01/04 22:24:07	1.15
***************
*** 2,6 ****
   * linux/mm/comp_cache/main.c
   *
!  * Time-stamp: <2002-01-02 10:33:08 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
--- 2,6 ----
   * linux/mm/comp_cache/main.c
   *
!  * Time-stamp: <2002-01-04 11:44:44 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
***************
*** 100,104 ****
  	}
  
- 	fragment->checksum = csum_partial(page_address(swap_cache_page), PAGE_SIZE, 0);
  	set_fragment_algorithm(fragment, algorithm);
  
--- 100,103 ----

Index: swapin.c
===================================================================
RCS file: /cvsroot/linuxcompressed/linux/mm/comp_cache/swapin.c,v
retrieving revision 1.11
retrieving revision 1.12
diff -C2 -r1.11 -r1.12
*** swapin.c	2002/01/02 16:59:06	1.11
--- swapin.c	2002/01/04 22:24:07	1.12
***************
*** 2,6 ****
   * linux/mm/comp_cache/swapin.c
   *
!  * Time-stamp: <2001-12-31 12:39:11 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
--- 2,6 ----
   * linux/mm/comp_cache/swapin.c
   *
!  * Time-stamp: <2002-01-04 11:44:53 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
***************
*** 40,46 ****
  	decompress(fragment_algorithm(fragment), page_address(comp_page->page) + fragment->offset, page_address(uncompressed_page));
  	
- 	if (fragment->checksum != csum_partial(page_address(uncompressed_page), PAGE_SIZE, 0))
- 		BUG();
- 
  	return;
  
--- 40,43 ----

Index: swapout.c
===================================================================
RCS file: /cvsroot/linuxcompressed/linux/mm/comp_cache/swapout.c,v
retrieving revision 1.13
retrieving revision 1.14
diff -C2 -r1.13 -r1.14
*** swapout.c	2002/01/02 16:59:06	1.13
--- swapout.c	2002/01/04 22:24:07	1.14
***************
*** 2,6 ****
   * linux/mm/comp_cache/swapout.c
   *
!  * Time-stamp: <2002-01-02 12:06:04 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
--- 2,6 ----
   * linux/mm/comp_cache/swapout.c
   *
!  * Time-stamp: <2002-01-03 17:24:51 rcastro>
   *  
   * Linux Virtual Memory Compressed Cache
***************
*** 146,150 ****
  swap_out_fragments(void) {
  	struct list_head * fragment_lh, * next_fragment;
! 	int maxscan, not_found;
  	comp_cache_fragment_t * fragment, * aux_fragment;
  	comp_cache_t * comp_page = NULL;
--- 146,150 ----
  swap_out_fragments(void) {
  	struct list_head * fragment_lh, * next_fragment;
! 	int maxscan;
  	comp_cache_fragment_t * fragment, * aux_fragment;
  	comp_cache_t * comp_page = NULL;
***************
*** 157,162 ****
  	next_fragment = &lru_queue;
  
! 	while (!list_empty(&lru_queue) && maxscan--) {
! 		fragment = list_entry(lru_queue.next, comp_cache_fragment_t, lru_queue);	
  
  		entry.val = fragment->index;
--- 157,162 ----
  	next_fragment = &lru_queue;
  
! 	while (!list_empty(&lru_queue) && maxscan--) {		
! 		fragment = list_entry(fragment_lh = lru_queue.next, comp_cache_fragment_t, lru_queue);	
  
  		entry.val = fragment->index;
***************
*** 172,175 ****
--- 172,176 ----
  				comp_cache_free(fragment);
  			page_cache_release(page);
+ 			maxscan++;
  			continue;
  		}
***************
*** 186,209 ****
  		swap_duplicate(entry);
  
! 		lock_page(page);
! 
! 		/* the fragment might have been freed while we slept
! 		 * for the lock above */
! 		not_found = 1;
! 		for_each_fragment(fragment_lh, comp_page)
! 			if (list_entry(fragment_lh, comp_cache_fragment_t, list) == fragment)
! 				not_found = 0;
! 
! 		/* if the fragment have been freed, forget it (even it
! 		 * has been reallocated to the same comp page, the
! 		 * fragment->index will be different because we hold a
! 		 * reference on the swp_entry */
! 		if (not_found || fragment->index != entry.val) {
! 			next_fragment = &lru_queue;
! 			maxscan = 10;
! 			UnlockPage(page);
  			goto freed;
  		}
! 		
  		swp_buffer = find_free_swp_buffer();
  		buffer_page = swp_buffer->comp_page->page;
--- 187,198 ----
  		swap_duplicate(entry);
  
! 		/* page locked? move it to the back of the list */
! 		if (TryLockPage(page)) {
! 			list_del(fragment_lh);
! 			list_add_tail(fragment_lh, &lru_queue);
! 			maxscan++;
  			goto freed;
  		}
! 
  		swp_buffer = find_free_swp_buffer();
  		buffer_page = swp_buffer->comp_page->page;
***************
*** 213,217 ****
  
  		/* race: this is not supposed to happen unless we
! 		 * sleep to lock the page in find_free_swp_buffer */
  		if (CompFragmentFreed(fragment)) {
  			free_swp_buffer(swp_buffer);
--- 202,206 ----
  
  		/* race: this is not supposed to happen unless we
! 		 * sleep to lock the page in find_free_swp_buffer() */
  		if (CompFragmentFreed(fragment)) {
  			free_swp_buffer(swp_buffer);