Messages in this thread | | | Subject | Re: [PATCH 3/3] mm: oom: show unreclaimable slab info when unreclaimable slabs > user memory | From | "Yang Shi" <> | Date | Thu, 05 Oct 2017 01:37:57 +0800 |
| |
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).
OK, sure.
> > [...] >> +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");
Thanks for pointing this. Will fix in new version.
Yang
> > 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 >
| |