The patch titled
swap: swap extent list is ordered
has been added to the -mm tree. Its filename is
swap-swap-extent-list-is-ordered.patch
Patches currently in -mm which might be from [EMAIL PROTECTED] are
swap-update-swapfile-i_sem-comment.patch
swap-correct-swapfile-nr_good_pages.patch
swap-move-destroy_swap_extents-calls.patch
swap-swap-extent-list-is-ordered.patch
swap-show-span-of-swap-extents.patch
swap-swap-unsigned-int-consistency.patch
swap-freeing-update-swap_listnext.patch
swap-get_swap_page-drop-swap_list_lock.patch
swap-scan_swap_map-restyled.patch
swap-scan_swap_map-drop-swap_device_lock.patch
swap-scan_swap_map-latency-breaks.patch
swap-swap_lock-replace-listdevice.patch
swap-update-swsusp-use-of-swap_info.patch
From: Hugh Dickins <[EMAIL PROTECTED]>
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]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
include/linux/swap.h | 2 --
mm/swapfile.c | 27 +++++++++------------------
2 files changed, 9 insertions(+), 20 deletions(-)
diff -puN include/linux/swap.h~swap-swap-extent-list-is-ordered
include/linux/swap.h
--- devel/include/linux/swap.h~swap-swap-extent-list-is-ordered 2005-07-08
22:34:44.000000000 -0700
+++ devel-akpm/include/linux/swap.h 2005-07-08 22:34:44.000000000 -0700
@@ -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;
diff -puN mm/swapfile.c~swap-swap-extent-list-is-ordered mm/swapfile.c
--- devel/mm/swapfile.c~swap-swap-extent-list-is-ordered 2005-07-08
22:34:44.000000000 -0700
+++ devel-akpm/mm/swapfile.c 2005-07-08 22:34:44.000000000 -0700
@@ -832,9 +832,9 @@ 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 */
@@ -859,10 +859,9 @@ 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,
@@ -872,16 +871,15 @@ 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;
}
/*
@@ -894,14 +892,7 @@ 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;
}
_
-
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