[Devel] [PATCH rh7 2/4] memcg: show correct mem/swap failcnt for beancounters

[Vladimir Davydov]

We should increment UB_PHYSPAGES failcnt if we failed to charge a page
and local reclaim does not help. We should also increment UB_SWAPPAGES
if there is no swap space left. However, currently we just show
memory.failcnt and memory.memsw.failcnt instead, which are incremented
anytime we fail to charge the corresponding resource counter no matter
if we eventually succeed reclaiming memcg or not. Fix this.

Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
 mm/memcontrol.c |   29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f164a94ca804..7d7c2e8fa145 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -281,6 +281,8 @@ struct mem_cgroup {
 
 	/* beancounter-related stats */
 	unsigned long long swap_max;
+	atomic_long_t mem_failcnt;
+	atomic_long_t swap_failcnt;
 
 	/*
 	 * Should the accounting and control be hierarchical, per subtree?
@@ -884,6 +886,18 @@ static void mem_cgroup_update_swap_max(struct mem_cgroup *memcg)
 		memcg->swap_max = swap;
 }
 
+static void mem_cgroup_inc_failcnt(struct mem_cgroup *memcg,
+				   gfp_t gfp_mask, unsigned int nr_pages)
+{
+	if (gfp_mask & __GFP_NOWARN)
+		return;
+
+	atomic_long_inc(&memcg->mem_failcnt);
+	if (do_swap_account &&
+	    res_counter_margin(&memcg->memsw) < nr_pages * PAGE_SIZE)
+		atomic_long_inc(&memcg->swap_failcnt);
+}
+
 static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg,
 					    enum mem_cgroup_events_index idx)
 {
@@ -2618,11 +2632,15 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	if (nr_pages > min_pages)
 		return CHARGE_RETRY;
 
-	if (!(gfp_mask & __GFP_WAIT))
+	if (!(gfp_mask & __GFP_WAIT)) {
+		mem_cgroup_inc_failcnt(mem_over_limit, gfp_mask, nr_pages);
 		return CHARGE_WOULDBLOCK;
+	}
 
-	if (gfp_mask & __GFP_NORETRY)
+	if (gfp_mask & __GFP_NORETRY) {
+		mem_cgroup_inc_failcnt(mem_over_limit, gfp_mask, nr_pages);
 		return CHARGE_NOMEM;
+	}
 
 	ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
 	if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
@@ -2649,6 +2667,9 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	/* If we don't need to call oom-killer at el, return immediately */
 	if (!oom_check)
 		return CHARGE_NOMEM;
+
+	mem_cgroup_inc_failcnt(mem_over_limit, gfp_mask, nr_pages);
+
 	/* check OOM */
 	if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask, get_order(csize)))
 		return CHARGE_OOM_DIE;
@@ -5139,7 +5160,7 @@ void mem_cgroup_fill_ub_parms(struct cgroup *cg,
 
 	p->held	= res_counter_read_u64(&memcg->res, RES_USAGE) >> PAGE_SHIFT;
 	p->maxheld = res_counter_read_u64(&memcg->res, RES_MAX_USAGE) >> PAGE_SHIFT;
-	p->failcnt = res_counter_read_u64(&memcg->res, RES_FAILCNT);
+	p->failcnt = atomic_long_read(&memcg->mem_failcnt);
 	lim = res_counter_read_u64(&memcg->res, RES_LIMIT);
 	lim = lim == RESOURCE_MAX ? UB_MAXVALUE :
 		min_t(unsigned long long, lim >> PAGE_SHIFT, UB_MAXVALUE);
@@ -5156,7 +5177,7 @@ void mem_cgroup_fill_ub_parms(struct cgroup *cg,
 	s->held	= res_counter_read_u64(&memcg->memsw, RES_USAGE) >> PAGE_SHIFT;
 	s->held -= p->held;
 	s->maxheld = memcg->swap_max >> PAGE_SHIFT;
-	s->failcnt = res_counter_read_u64(&memcg->memsw, RES_FAILCNT);
+	s->failcnt = atomic_long_read(&memcg->swap_failcnt);
 	lim = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
 	lim = lim == RESOURCE_MAX ? UB_MAXVALUE :
 		min_t(unsigned long long, lim >> PAGE_SHIFT, UB_MAXVALUE);
-- 
1.7.10.4