memcg: better migration handling
This patch changes page migration under memory controller to use a
different algorithm. (thanks to Christoph for new idea.)
Before:
- page_cgroup is migrated from an old page to a new page.
After:
- a new page is accounted , no reuse of page_cgroup.
Pros:
- We can avoid compliated lock depndencies and races in migration.
Cons:
- new param to mem_cgroup_charge_common().
- mem_cgroup_getref() is added for handling ref_cnt ping-pong.
This version simplifies complicated lock dependency in page migraiton
under memory resource controller.
new refcnt sequence is following.
a mapped page:
prepage_migration() ..... +1 to NEW page
try_to_unmap() ..... all refs to OLD page is gone.
move_pages() ..... +1 to NEW page if page cache.
remap... ..... all refs from *map* is added to NEW one.
end_migration() ..... -1 to New page.
page's mapcount + (page_is_cache) refs are added to NEW one.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/migrate.c b/mm/migrate.c
index 376cceb..f6d7f8e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -358,6 +358,10 @@
__inc_zone_page_state(newpage, NR_FILE_PAGES);
write_unlock_irq(&mapping->tree_lock);
+ if (!PageSwapCache(newpage)) {
+ mem_cgroup_uncharge_page(page);
+ mem_cgroup_getref(newpage);
+ }
return 0;
}
@@ -611,7 +615,6 @@
rc = fallback_migrate_page(mapping, newpage, page);
if (!rc) {
- mem_cgroup_page_migration(page, newpage);
remove_migration_ptes(page, newpage);
} else
newpage->mapping = NULL;
@@ -641,6 +644,14 @@
/* page was freed from under us. So we are done. */
goto move_newpage;
+ charge = mem_cgroup_prepare_migration(page, newpage);
+ if (charge == -ENOMEM) {
+ rc = -ENOMEM;
+ goto move_newpage;
+ }
+ /* prepare cgroup just returns 0 or -ENOMEM */
+ BUG_ON(charge);
+
rc = -EAGAIN;
if (TestSetPageLocked(page)) {
if (!force)
@@ -692,19 +703,14 @@
goto rcu_unlock;
}
- charge = mem_cgroup_prepare_migration(page);
/* Establish migration ptes or remove ptes */
try_to_unmap(page, 1);
if (!page_mapped(page))
rc = move_to_new_page(newpage, page);
- if (rc) {
+ if (rc)
remove_migration_ptes(page, page);
- if (charge)
- mem_cgroup_end_migration(page);
- } else if (charge)
- mem_cgroup_end_migration(newpage);
rcu_unlock:
if (rcu_locked)
rcu_read_unlock();
@@ -725,6 +731,8 @@
}
move_newpage:
+ if (!charge)
+ mem_cgroup_end_migration(newpage);
/*
* Move the new page to the LRU. If migration was not successful
* then this will free the page.