[PATCH 2/2] mm: oom: dump single excessive slab cache when oom

["Yang Shi" <yang.s@alibaba-inc.com>]

Per the discussion with David [1], it looks more reasonable to just dump
the single excessive slab cache instead of dumping all slab caches when
oom.

Dump single excessive slab cache if its size is > 10% of total system
memory size when oom regardless it is unreclaimable.

[1] https://marc.info/?l=linux-mm&m=150819933626604&w=2

Suggested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
---
 mm/oom_kill.c    | 22 +---------------------
 mm/slab.h        |  4 ++--
 mm/slab_common.c | 21 ++++++++++++++++-----
 3 files changed, 19 insertions(+), 28 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 26add8a..f996f29 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -162,25 +162,6 @@ static bool oom_unkillable_task(struct task_struct *p,
 	return false;
 }
 
-/*
- * Print out unreclaimble slabs info when unreclaimable slabs amount is greater
- * than all user memory (LRU pages)
- */
-static bool is_dump_unreclaim_slabs(void)
-{
-	unsigned long nr_lru;
-
-	nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
-		 global_node_page_state(NR_INACTIVE_ANON) +
-		 global_node_page_state(NR_ACTIVE_FILE) +
-		 global_node_page_state(NR_INACTIVE_FILE) +
-		 global_node_page_state(NR_ISOLATED_ANON) +
-		 global_node_page_state(NR_ISOLATED_FILE) +
-		 global_node_page_state(NR_UNEVICTABLE);
-
-	return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru);
-}
-
 /**
  * oom_badness - heuristic function to determine which candidate task to kill
  * @p: task struct of which task we should calculate
@@ -443,8 +424,7 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
 		mem_cgroup_print_oom_info(oc->memcg, p);
 	else {
 		show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
-		if (is_dump_unreclaim_slabs())
-			dump_unreclaimable_slab();
+		dump_slab_cache();
 	}
 	if (sysctl_oom_dump_tasks)
 		dump_tasks(oc->memcg, oc->nodemask);
diff --git a/mm/slab.h b/mm/slab.h
index 6a86025..818b569 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -507,9 +507,9 @@ static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
 int memcg_slab_show(struct seq_file *m, void *p);
 
 #if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)
-void dump_unreclaimable_slab(void);
+void dump_slab_cache(void);
 #else
-static inline void dump_unreclaimable_slab(void)
+static inline void dump_slab_cache(void)
 {
 }
 #endif
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 1b14fe0..e5bfa07 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1311,7 +1311,18 @@ static int slab_show(struct seq_file *m, void *p)
 	return 0;
 }
 
-void dump_unreclaimable_slab(void)
+static bool inline is_dump_slabs(struct kmem_cache *s, struct slabinfo *sinfo)
+{
+	unsigned long total = 0, reserved = 0, highmem = 0;
+	unsigned long slab_size = sinfo->num_objs * s->size;
+
+	calc_mem_size(&total, &reserved, &highmem);
+
+	/* Check if single slab > 10% of total memory size */
+	return (slab_size > (total * PAGE_SIZE / 10));
+}
+
+void dump_slab_cache(void)
 {
 	struct kmem_cache *s, *s2;
 	struct slabinfo sinfo;
@@ -1324,20 +1335,20 @@ void dump_unreclaimable_slab(void)
 	 * without acquiring the mutex.
 	 */
 	if (!mutex_trylock(&slab_mutex)) {
-		pr_warn("excessive unreclaimable slab but cannot dump stats\n");
+		pr_warn("excessive slab cache but cannot dump stats\n");
 		return;
 	}
 
-	pr_info("Unreclaimable slab info:\n");
+	pr_info("The list of excessive single slab cache:\n");
 	pr_info("Name                      Used          Total\n");
 
 	list_for_each_entry_safe(s, s2, &slab_caches, list) {
-		if (!is_root_cache(s) || (s->flags & SLAB_RECLAIM_ACCOUNT))
+		if (!is_root_cache(s))
 			continue;
 
 		get_slabinfo(s, &sinfo);
 
-		if (sinfo.num_objs > 0)
+		if (is_dump_slabs(s, &sinfo))
 			pr_info("%-17s %10luKB %10luKB\n", cache_name(s),
 				(sinfo.active_objs * s->size) / 1024,
 				(sinfo.num_objs * s->size) / 1024);
-- 
1.8.3.1