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[209.85.220.65]) by mx.google.com with SMTPS id y68sor746800iof.126.2019.07.02.22.57.28 for (Google Transport Security); Tue, 02 Jul 2019 22:57:28 -0700 (PDT) Received-SPF: pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=ivq82QwW; spf=pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=PTN5uwIluYymv/ulqvQOLWr4+wOTebEj5XIObY2vSeY=; b=ivq82QwW1tBdSlDYTid675w54Gbz4CQCGJTmihhEtqYZBfXWihXITmK6S+OQZLda+m TiNO6mW83zAkPUhfhHjeosSE+H8TTzK7CcVGSGrCF+pF3ZxdcFzOMQdY0nYkGPAVDFRd e1kgz2aKBHB02Zbju5LVXeLHuMzg9HEwdiFSIdx9+mhao6rwXe7KFu20WIcB1ZNITXko nOjj+nGebTbbqf9A+NwYhGhCA+Wxo2P8BwyJwlhVaDMKQ8AvXsFU+IoST7N1xpJsWMcG HmI0fPFui78cE8Ge0Tp9f/K4iKgk2U+WHDKwCdLNXUs5lbYZxijD7x2Gmty3ODDv5WT8 W3XA== X-Google-Smtp-Source: APXvYqyN/NV/RdaUqJ4Cw6ivKuwHLkZE29oXG/lYctkt9LNUUwhaGULtS9fnlWD8Xz3dAOScg12AObmcKyKLuAvKnrg= X-Received: by 2002:a6b:8dcf:: with SMTP id p198mr5666129iod.46.1562133448460; Tue, 02 Jul 2019 22:57:28 -0700 (PDT) MIME-Version: 1.0 References: <1562116978-19539-1-git-send-email-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Wed, 3 Jul 2019 13:56:52 +0800 Message-ID: Subject: Re: [PATCH] mm/memcontrol: fix wrong statistics in memory.stat To: Shakeel Butt Cc: Andrew Morton , Linux MM , Michal Hocko , Yafang Shao Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jul 3, 2019 at 1:17 PM Shakeel Butt wrote: > > On Tue, Jul 2, 2019 at 9:28 PM Yafang Shao wrote: > > > > On Wed, Jul 3, 2019 at 11:50 AM Shakeel Butt wrote: > > > > > > +Johannes Weiner > > > > > > On Tue, Jul 2, 2019 at 6:23 PM Yafang Shao wrote: > > > > > > > > When we calculate total statistics for memcg1_stats and memcg1_events, we > > > > use the the index 'i' in the for loop as the events index. > > > > Actually we should use memcg1_stats[i] and memcg1_events[i] as the > > > > events index. > > > > > > > > Fixes: 8de7ecc6483b ("memcg: reduce memcg tree traversals for stats collection") > > > > > > Actually it fixes 42a300353577 ("mm: memcontrol: fix recursive > > > statistics correctness & scalabilty"). > > > > > > > Hi Shakeel, > > > > In 8de7ecc6483b, this code was changed from memcg_page_state(mi, > > memcg1_stats[i]) to acc.stat[i]. > > > > - for_each_mem_cgroup_tree(mi, memcg) > > - val += memcg_page_state(mi, memcg1_stats[i]) * > > - PAGE_SIZE; > > - seq_printf(m, "total_%s %llu\n", memcg1_stat_names[i], val); > > + seq_printf(m, "total_%s %llu\n", memcg1_stat_names[i], > > + (u64)acc.stat[i] * PAGE_SIZE); > > > > In 42a300353577, this code was changed from acc.vmstats[i] to > > memcg_events(memcg, i). > > - (u64)acc.vmstats[i] * PAGE_SIZE); > > + (u64)memcg_page_state(memcg, i) * PAGE_SIZE); > > > > So seems this issue was introduced in 8de7ecc6483b, isn't it ? > > > > > > That's the reason I said 8de7ecc6483b made it subtle but not wrong. > Check accumulate_memcg_tree() in 8de7ecc6483b, the memcg_page_state() > and memcg_events() are called with correct index but saved at 'i' > index in acc array. > Got it. Thanks for your explanation and review. Thanks Yafang > > > > > Signed-off-by: Yafang Shao > > > > Cc: Shakeel Butt > > > > Cc: Michal Hocko > > > > Cc: Yafang Shao > > > > --- > > > > mm/memcontrol.c | 5 +++-- > > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > > index 3ee806b..2ad94d0 100644 > > > > --- a/mm/memcontrol.c > > > > +++ b/mm/memcontrol.c > > > > @@ -3528,12 +3528,13 @@ static int memcg_stat_show(struct seq_file *m, void *v) > > > > if (memcg1_stats[i] == MEMCG_SWAP && !do_memsw_account()) > > > > continue; > > > > seq_printf(m, "total_%s %llu\n", memcg1_stat_names[i], > > > > - (u64)memcg_page_state(memcg, i) * PAGE_SIZE); > > > > + (u64)memcg_page_state(memcg, memcg1_stats[i]) * > > > > + PAGE_SIZE); > > > > > > It seems like I made the above very subtle in 8de7ecc6483b and > > > Johannes missed this subtlety in 42a300353577 (and I missed it in the > > > review). > > > > > > > } > > > > > > > > for (i = 0; i < ARRAY_SIZE(memcg1_events); i++) > > > > seq_printf(m, "total_%s %llu\n", memcg1_event_names[i], > > > > - (u64)memcg_events(memcg, i)); > > > > + (u64)memcg_events(memcg, memcg1_events[i])); > > > > > > > > for (i = 0; i < NR_LRU_LISTS; i++) > > > > seq_printf(m, "total_%s %llu\n", mem_cgroup_lru_names[i], > > > > -- > > > > 1.8.3.1 > > > > > > > > > > Reviewed-by: Shakeel Butt