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authorBo Liu <bo-liu@hotmail.com>2009-11-02 16:50:33 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2009-11-09 16:22:33 -0800
commit82a90819b2992515f794b032ee7d75fba4771e33 (patch)
tree3ed29968b7ef393d135ac435116fa3b71c73aafc /mm
parentcd4ad4b9dda686bce57f939671cc066a554b7f92 (diff)
mm: remove incorrect swap_count() from try_to_unuse()
commit 32c5fc10e79a7053ac5728b01a0bff55cbcb9d49 upstream. In try_to_unuse(), swcount is a local copy of *swap_map, including the SWAP_HAS_CACHE bit; but a wrong comparison against swap_count(*swap_map), which masks off the SWAP_HAS_CACHE bit, succeeded where it should fail. That had the effect of resetting the mm from which to start searching for the next swap page, to an irrelevant mm instead of to an mm in which this swap page had been found: which may increase search time by ~20%. But we're used to swapoff being slow, so never noticed the slowdown. Remove that one spurious use of swap_count(): Bo Liu thought it merely redundant, Hugh rewrote the description since it was measurably wrong. Signed-off-by: Bo Liu <bo-liu@hotmail.com> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm')
-rw-r--r--mm/swapfile.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8ffdc0d23c53..b47ccd77f050 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1149,8 +1149,7 @@ static int try_to_unuse(unsigned int type)
} else
retval = unuse_mm(mm, entry, page);
- if (set_start_mm &&
- swap_count(*swap_map) < swcount) {
+ if (set_start_mm && *swap_map < swcount) {
mmput(new_start_mm);
atomic_inc(&mm->mm_users);
new_start_mm = mm;