>From 257a1e6603aab8c6a3bd25648872a11e8b85ef64 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Date: Thu, 28 Jun 2012 19:07:24 +0900
Subject: [PATCH 2/2]
For handling many kinds of races, memcg adds an extra charge to
page's memcg at page migration. But this affects the page compaction
and make it fail if the memcg is under OOM.
This patch uses res_counter_charge_nofail() in page migration path
and remove -ENOMEM. By this, page migration will not fail by the
status of memcg.
Even though res_counter_charge_nofail can silently go over the memcg
limit mem_cgroup_usage compensates that and it doesn't tell the real truth
to the userspace.
Excessive charges are only temporal and done on a single page per-CPU in
the worst case. This sounds tolerable and actually consumes less charges
than the current per-cpu memcg_stock.
Changelog:
- added Michal's comment to patch description.
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Reported-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
mm/memcontrol.c | 26 +++++++-------------------
1 files changed, 7 insertions(+), 19 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b11fb2f..00f7cc2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3168,6 +3168,7 @@ int mem_cgroup_prepare_migration(struct page *page,
struct page *newpage, struct mem_cgroup **memcgp, gfp_t gfp_mask)
{
struct mem_cgroup *memcg = NULL;
+ struct res_counter *dummy;
struct page_cgroup *pc;
enum charge_type ctype;
int ret = 0;
@@ -3222,29 +3223,16 @@ int mem_cgroup_prepare_migration(struct page *page,
*/
if (!memcg)
return 0;
-
- *memcgp = memcg;
- ret = __mem_cgroup_try_charge(NULL, gfp_mask, 1, memcgp, false);
- css_put(&memcg->css);/* drop extra refcnt */
- if (ret) {
- if (PageAnon(page)) {
- lock_page_cgroup(pc);
- ClearPageCgroupMigration(pc);
- unlock_page_cgroup(pc);
- /*
- * The old page may be fully unmapped while we kept it.
- */
- mem_cgroup_uncharge_page(page);
- }
- /* we'll need to revisit this error code (we have -EINTR) */
- return -ENOMEM;
- }
/*
* We charge new page before it's used/mapped. So, even if unlock_page()
* is called before end_migration, we can catch all events on this new
* page. In the case new page is migrated but not remapped, new page's
* mapcount will be finally 0 and we call uncharge in end_migration().
*/
+ res_counter_charge_nofail(&memcg->res, PAGE_SIZE, &dummy);
+ if (do_swap_account)
+ res_counter_charge_nofail(&memcg->memsw, PAGE_SIZE, &dummy);
+
if (PageAnon(page))
ctype = MEM_CGROUP_CHARGE_TYPE_ANON;
else if (page_is_file_cache(page))
@@ -3813,9 +3801,9 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
if (!mem_cgroup_is_root(memcg)) {
if (!swap)
- return res_counter_read_u64(&memcg->res, RES_USAGE);
+ return res_counter_usage_safe(&memcg->res);
else
- return res_counter_read_u64(&memcg->memsw, RES_USAGE);
+ return res_counter_usage_safe(&memcg->memsw);
}
val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE);
--
1.7.4.1
--
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