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/memcontrol.c b/mm/memcontrol.c
index c878b1c..f858615 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6307,7 +6307,7 @@
* Because lookup_swap_cache() updates some statistics counter,
* we call find_get_page() with swapper_space directly.
*/
- page = find_get_page(&swapper_space, ent.val);
+ page = find_get_page(swap_address_space(ent), ent.val);
if (do_swap_account)
entry->val = ent.val;
@@ -6348,7 +6348,7 @@
swp_entry_t swap = radix_to_swp_entry(page);
if (do_swap_account)
*entry = swap;
- page = find_get_page(&swapper_space, swap.val);
+ page = find_get_page(swap_address_space(swap), swap.val);
}
#endif
return page;