Messages in this thread | | | Date | Wed, 4 Oct 2017 16:27:36 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH 3/3] mm: oom: show unreclaimable slab info when unreclaimable slabs > user memory |
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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).
[...] > +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
-- Michal Hocko SUSE Labs
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