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 <[EMAIL PROTECTED]>
---
include/linux/swap.h | 2 --
mm/swapfile.c | 27 +++++++++------------------
2 files changed, 9 insertions(+), 20 deletions(-)
--- swap3/include/linux/swap.h 2005-07-07 12:33:21.000000000 +0100
+++ swap4/include/linux/swap.h 2005-07-08 19:14:00.000000000 +0100
@@ -115,8 +115,6 @@ enum {
/*
* The in-memory structure used to track swap areas.
- * extent_list.prev points at the lowest-index extent. That list is
- * sorted.
*/
struct swap_info_struct {
unsigned int flags;
--- swap3/mm/swapfile.c 2005-07-08 19:13:46.000000000 +0100
+++ swap4/mm/swapfile.c 2005-07-08 19:14:00.000000000 +0100
@@ -830,9 +830,9 @@ sector_t map_swap_page(struct swap_info_
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 */
@@ -857,10 +857,9 @@ static void destroy_swap_extents(struct
/*
* 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,
@@ -870,16 +869,15 @@ add_swap_extent(struct swap_info_struct
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;
}
/*
@@ -892,14 +890,7 @@ add_swap_extent(struct swap_info_struct
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;
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
