swap: make each swap partition have one address_space
When I use several fast SSD to do swap, swapper_space.tree_lock is
heavily contended. This makes each swap partition have one
address_space to reduce the lock contention. There is an array of
address_space for swap. The swap entry type is the index to the array.
In my test with 3 SSD, this increases the swapout throughput 20%.
[akpm@linux-foundation.org: revert unneeded change to __add_to_swap_cache]
Signed-off-by: Shaohua Li <shli@fusionio.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mincore.c b/mm/mincore.c
index 936b4ce..da2be56 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -75,7 +75,7 @@
/* shmem/tmpfs may return swap: account for swapcache page too. */
if (radix_tree_exceptional_entry(page)) {
swp_entry_t swap = radix_to_swp_entry(page);
- page = find_get_page(&swapper_space, swap.val);
+ page = find_get_page(swap_address_space(swap), swap.val);
}
#endif
if (page) {
@@ -135,7 +135,8 @@
} else {
#ifdef CONFIG_SWAP
pgoff = entry.val;
- *vec = mincore_page(&swapper_space, pgoff);
+ *vec = mincore_page(swap_address_space(entry),
+ pgoff);
#else
WARN_ON(1);
*vec = 1;