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| author | Hugh Dickins <hugh@veritas.com> | 2005-09-03 15:54:34 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@evo.osdl.org> | 2005-09-05 00:05:40 -0700 |
| commit | 11d31886dbcb61039ed3789e583d21c6e70960fd (patch) | |
| tree | ddaebfd35080a530a30c56587707c2c5ef452591 /mm/swapfile.c | |
| parent | 4cd3bb10ff0b21b77b5a4cd13b4bd36694e054c4 (diff) | |
| download | linux-3.10-11d31886dbcb61039ed3789e583d21c6e70960fd.tar.gz linux-3.10-11d31886dbcb61039ed3789e583d21c6e70960fd.tar.bz2 linux-3.10-11d31886dbcb61039ed3789e583d21c6e70960fd.zip | |
[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/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 27 |
1 files changed, 9 insertions, 18 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 4b39e9501d4..73521d39e98 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; } |