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authorHugh Dickins <hugh@veritas.com>2005-09-03 15:54:34 -0700
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 00:05:40 -0700
commit11d31886dbcb61039ed3789e583d21c6e70960fd (patch)
treeddaebfd35080a530a30c56587707c2c5ef452591 /mm
parent4cd3bb10ff0b21b77b5a4cd13b4bd36694e054c4 (diff)
downloadlinux-sh-11d31886dbcb61039ed3789e583d21c6e70960fd.tar.gz
[PATCH] swap: swap extent list is ordered
There are several comments that swap's extent_list.prev points to the lowest extent: that's not so, it's extent_list.next which points to it, as you'd expect. And a couple of loops in add_swap_extent which go all the way through the list, when they should just add to the other end. Fix those up, and let map_swap_page search the list forwards: profiles shows it to be twice as quick that way - because prefetch works better on how the structs are typically kmalloc'ed? or because usually more is written to than read from swap, and swap is allocated ascendingly? Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/swapfile.c27
1 files changed, 9 insertions, 18 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 4b39e9501d44..73521d39e985 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -832,9 +832,9 @@ sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
offset < (se->start_page + se->nr_pages)) {
return se->start_block + (offset - se->start_page);
}
- lh = se->list.prev;
+ lh = se->list.next;
if (lh == &sis->extent_list)
- lh = lh->prev;
+ lh = lh->next;
se = list_entry(lh, struct swap_extent, list);
sis->curr_swap_extent = se;
BUG_ON(se == start_se); /* It *must* be present */
@@ -859,10 +859,9 @@ static void destroy_swap_extents(struct swap_info_struct *sis)
/*
* Add a block range (and the corresponding page range) into this swapdev's
- * extent list. The extent list is kept sorted in block order.
+ * extent list. The extent list is kept sorted in page order.
*
- * This function rather assumes that it is called in ascending sector_t order.
- * It doesn't look for extent coalescing opportunities.
+ * This function rather assumes that it is called in ascending page order.
*/
static int
add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
@@ -872,16 +871,15 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
struct swap_extent *new_se;
struct list_head *lh;
- lh = sis->extent_list.next; /* The highest-addressed block */
- while (lh != &sis->extent_list) {
+ lh = sis->extent_list.prev; /* The highest page extent */
+ if (lh != &sis->extent_list) {
se = list_entry(lh, struct swap_extent, list);
- if (se->start_block + se->nr_pages == start_block &&
- se->start_page + se->nr_pages == start_page) {
+ BUG_ON(se->start_page + se->nr_pages != start_page);
+ if (se->start_block + se->nr_pages == start_block) {
/* Merge it */
se->nr_pages += nr_pages;
return 0;
}
- lh = lh->next;
}
/*
@@ -894,14 +892,7 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
new_se->nr_pages = nr_pages;
new_se->start_block = start_block;
- lh = sis->extent_list.prev; /* The lowest block */
- while (lh != &sis->extent_list) {
- se = list_entry(lh, struct swap_extent, list);
- if (se->start_block > start_block)
- break;
- lh = lh->prev;
- }
- list_add_tail(&new_se->list, lh);
+ list_add_tail(&new_se->list, &sis->extent_list);
sis->nr_extents++;
return 0;
}