From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id AEE676B0253 for ; Wed, 4 Oct 2017 14:09:00 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id r83so27770478pfj.5 for ; Wed, 04 Oct 2017 11:09:00 -0700 (PDT) Received: from out0-194.mail.aliyun.com (out0-194.mail.aliyun.com. [140.205.0.194]) by mx.google.com with ESMTPS id v8si3863029plp.86.2017.10.04.11.08.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 04 Oct 2017 11:08:59 -0700 (PDT) Subject: Re: [PATCH 3/3] mm: oom: show unreclaimable slab info when unreclaimable slabs > user memory References: <1507053977-116952-1-git-send-email-yang.s@alibaba-inc.com> <1507053977-116952-4-git-send-email-yang.s@alibaba-inc.com> <20171004142736.u4z7zdar6g7bqgrj@dhcp22.suse.cz> From: "Yang Shi" Message-ID: <4b668145-a81d-6f46-0569-b0adb76788d8@alibaba-inc.com> Date: Thu, 05 Oct 2017 02:08:48 +0800 MIME-Version: 1.0 In-Reply-To: <20171004142736.u4z7zdar6g7bqgrj@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org 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 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org