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/swapfile.c b/mm/swapfile.c
index e97a0e5..e51864e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -79,7 +79,7 @@
struct page *page;
int ret = 0;
- page = find_get_page(&swapper_space, entry.val);
+ page = find_get_page(swap_address_space(entry), entry.val);
if (!page)
return 0;
/*
@@ -699,7 +699,8 @@
p = swap_info_get(entry);
if (p) {
if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
- page = find_get_page(&swapper_space, entry.val);
+ page = find_get_page(swap_address_space(entry),
+ entry.val);
if (page && !trylock_page(page)) {
page_cache_release(page);
page = NULL;