On 10/4/17 7:27 AM, Michal Hocko wrote:
On Wed 04-10-17 02:06:17, Yang Shi wrote:
+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);
+}
I am sorry I haven't pointed this earlier (I was following only half
way) but this should really be memcg aware. You are checking only global
counters. I do not think it is an absolute must to provide per-memcg
data but you should at least check !is_memcg_oom(oc).
BTW, I saw there is already such check in dump_header that looks like
the below code:
if (oc->memcg)
mem_cgroup_print_oom_info(oc->memcg, p);
else
show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
I'm supposed it'd better to replace "oc->memcg" to "is_memcg_oom(oc)"
since they do the same check and "is_memcg_oom" interface sounds preferable.
Then I'm going to move unreclaimable slabs dump to the "else" block.
Yang
[...]
+void dump_unreclaimable_slab(void)
+{
+ struct kmem_cache *s, *s2;
+ struct slabinfo sinfo;
+
+ pr_info("Unreclaimable slab info:\n");
+ pr_info("Name Used Total\n");
+
+ /*
+ * Here acquiring slab_mutex is risky since we don't prefer to get
+ * sleep in oom path. But, without mutex hold, it may introduce a
+ * risk of crash.
+ * Use mutex_trylock to protect the list traverse, dump nothing
+ * without acquiring the mutex.
+ */
+ if (!mutex_trylock(&slab_mutex))
+ return;
I would move the trylock up so that we do not get empty and confusing
Unreclaimable slab info: and add a note that we are not dumping anything
due to lock contention
pr_warn("excessive unreclaimable slab memory but cannot dump stats to give
you more details\n");
Other than that this looks sensible to me.
+ list_for_each_entry_safe(s, s2, &slab_caches, list) {
+ if (!is_root_cache(s) || (s->flags & SLAB_RECLAIM_ACCOUNT))
+ continue;
+
+ memset(&sinfo, 0, sizeof(sinfo));
+ get_slabinfo(s, &sinfo);
+
+ if (sinfo.num_objs > 0)
+ pr_info("%-17s %10luKB %10luKB\n", cache_name(s),
+ (sinfo.active_objs * s->size) / 1024,
+ (sinfo.num_objs * s->size) / 1024);
+ }
+ mutex_unlock(&slab_mutex);
+}
+
#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
void *memcg_slab_start(struct seq_file *m, loff_t *pos)
{
--
1.8.3.1
