memcg: fix reclaimable lru check in memcg

Now, in mem_cgroup_hierarchical_reclaim(), mem_cgroup_local_usage() is
used for checking whether the memcg contains reclaimable pages or not.  If
no pages in it, the routine skips it.

But, mem_cgroup_local_usage() contains Unevictable pages and cannot handle
"noswap" condition correctly.  This doesn't work on a swapless system.

This patch adds test_mem_cgroup_reclaimable() and replaces
mem_cgroup_local_usage().  test_mem_cgroup_reclaimable() see LRU counter
and returns correct answer to the caller.  And this new function has
"noswap" argument and can see only FILE LRU if necessary.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix kerneldoc layout]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Ying Han <yinghan@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
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 ddffc74..a7a5cb1 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -577,15 +577,6 @@ static long mem_cgroup_read_stat(struct mem_cgroup *mem,
        return val;
 }
 
-static long mem_cgroup_local_usage(struct mem_cgroup *mem)
-{
-       long ret;
-
-       ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
-       ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
-       return ret;
-}
-
 static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
                                         bool charge)
 {
@@ -1129,7 +1120,6 @@ unsigned long mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg,
        return MEM_CGROUP_ZSTAT(mz, lru);
 }
 
-#ifdef CONFIG_NUMA
 static unsigned long mem_cgroup_node_nr_file_lru_pages(struct mem_cgroup *memcg,
                                                        int nid)
 {
@@ -1141,6 +1131,17 @@ static unsigned long mem_cgroup_node_nr_file_lru_pages(struct mem_cgroup *memcg,
        return ret;
 }
 
+static unsigned long mem_cgroup_node_nr_anon_lru_pages(struct mem_cgroup *memcg,
+                                                       int nid)
+{
+       unsigned long ret;
+
+       ret = mem_cgroup_get_zonestat_node(memcg, nid, LRU_INACTIVE_ANON) +
+               mem_cgroup_get_zonestat_node(memcg, nid, LRU_ACTIVE_ANON);
+       return ret;
+}
+
+#if MAX_NUMNODES > 1
 static unsigned long mem_cgroup_nr_file_lru_pages(struct mem_cgroup *memcg)
 {
        u64 total = 0;
@@ -1152,17 +1153,6 @@ static unsigned long mem_cgroup_nr_file_lru_pages(struct mem_cgroup *memcg)
        return total;
 }
 
-static unsigned long mem_cgroup_node_nr_anon_lru_pages(struct mem_cgroup *memcg,
-                                                       int nid)
-{
-       unsigned long ret;
-
-       ret = mem_cgroup_get_zonestat_node(memcg, nid, LRU_INACTIVE_ANON) +
-               mem_cgroup_get_zonestat_node(memcg, nid, LRU_ACTIVE_ANON);
-
-       return ret;
-}
-
 static unsigned long mem_cgroup_nr_anon_lru_pages(struct mem_cgroup *memcg)
 {
        u64 total = 0;
@@ -1559,6 +1549,28 @@ mem_cgroup_select_victim(struct mem_cgroup *root_mem)
        return ret;
 }
 
+/**
+ * test_mem_cgroup_node_reclaimable
+ * @mem: the target memcg
+ * @nid: the node ID to be checked.
+ * @noswap : specify true here if the user wants flle only information.
+ *
+ * This function returns whether the specified memcg contains any
+ * reclaimable pages on a node. Returns true if there are any reclaimable
+ * pages in the node.
+ */
+static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *mem,
+               int nid, bool noswap)
+{
+       if (mem_cgroup_node_nr_file_lru_pages(mem, nid))
+               return true;
+       if (noswap || !total_swap_pages)
+               return false;
+       if (mem_cgroup_node_nr_anon_lru_pages(mem, nid))
+               return true;
+       return false;
+
+}
 #if MAX_NUMNODES > 1
 
 /*
@@ -1580,15 +1592,8 @@ static void mem_cgroup_may_update_nodemask(struct mem_cgroup *mem)
 
        for_each_node_mask(nid, node_states[N_HIGH_MEMORY]) {
 
-               if (mem_cgroup_get_zonestat_node(mem, nid, LRU_INACTIVE_FILE) ||
-                   mem_cgroup_get_zonestat_node(mem, nid, LRU_ACTIVE_FILE))
-                       continue;
-
-               if (total_swap_pages &&
-                   (mem_cgroup_get_zonestat_node(mem, nid, LRU_INACTIVE_ANON) ||
-                    mem_cgroup_get_zonestat_node(mem, nid, LRU_ACTIVE_ANON)))
-                       continue;
-               node_clear(nid, mem->scan_nodes);
+               if (!test_mem_cgroup_node_reclaimable(mem, nid, false))
+                       node_clear(nid, mem->scan_nodes);
        }
 }
 
@@ -1627,11 +1632,51 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
        return node;
 }
 
+/*
+ * Check all nodes whether it contains reclaimable pages or not.
+ * For quick scan, we make use of scan_nodes. This will allow us to skip
+ * unused nodes. But scan_nodes is lazily updated and may not cotain
+ * enough new information. We need to do double check.
+ */
+bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
+{
+       int nid;
+
+       /*
+        * quick check...making use of scan_node.
+        * We can skip unused nodes.
+        */
+       if (!nodes_empty(mem->scan_nodes)) {
+               for (nid = first_node(mem->scan_nodes);
+                    nid < MAX_NUMNODES;
+                    nid = next_node(nid, mem->scan_nodes)) {
+
+                       if (test_mem_cgroup_node_reclaimable(mem, nid, noswap))
+                               return true;
+               }
+       }
+       /*
+        * Check rest of nodes.
+        */
+       for_each_node_state(nid, N_HIGH_MEMORY) {
+               if (node_isset(nid, mem->scan_nodes))
+                       continue;
+               if (test_mem_cgroup_node_reclaimable(mem, nid, noswap))
+                       return true;
+       }
+       return false;
+}
+
 #else
 int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
 {
        return 0;
 }
+
+bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
+{
+       return test_mem_cgroup_node_reclaimable(mem, 0, noswap);
+}
 #endif
 
 /*
@@ -1702,7 +1747,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
                                }
                        }
                }
-               if (!mem_cgroup_local_usage(victim)) {
+               if (!mem_cgroup_reclaimable(victim, noswap)) {
                        /* this cgroup's local usage == 0 */
                        css_put(&victim->css);
                        continue;