From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12437C3A5A0 for ; Mon, 19 Aug 2019 22:29:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D166B22CEC for ; Mon, 19 Aug 2019 22:29:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566253741; bh=RlMWA2jWrh1pT0quIb2OrO6Q4GbS72Ihhicw5U0G4E4=; h=Date:From:To:Subject:List-ID:From; b=yfQd0aX3LvwUby93QU6HJ00PAMJQsM5Wm86x2OffSPLVafIZLTBWSTSTUzqKKvt+B 88sqjDMf8uwYXK1MiUUv6vHZ3o33z6QWXblyP5sgAgbaKw515BCOxSX7cU3uZXygLg WT7erLC6peKmEyysW+zvZ3vIvv/iyRIKpv1Mj1dU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728618AbfHSW3B (ORCPT ); Mon, 19 Aug 2019 18:29:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:37428 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728438AbfHSW3A (ORCPT ); Mon, 19 Aug 2019 18:29:00 -0400 Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1CC4E22CE8; Mon, 19 Aug 2019 22:29:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566253740; bh=RlMWA2jWrh1pT0quIb2OrO6Q4GbS72Ihhicw5U0G4E4=; h=Date:From:To:Subject:From; b=E1PnUH4AVwVpnbV/R1nunxhRuMWti90d2RAVFGipyfNWJP/u31laEXeN8izlNHON+ /jHNFVwQMjDGuWegCd8Q59xOIPLZGNq+1PoecJo6iDohH7oIe0j1uKMUxIot6Je+o2 8SjlmFbb8Ozc75yxCfwkf7PcxfTfs7FmnIzuQZ6M= Date: Mon, 19 Aug 2019 15:28:58 -0700 From: akpm@linux-foundation.org To: mm-commits@vger.kernel.org, vdavydov.dev@gmail.com, stable@vger.kernel.org, mhocko@suse.com, hannes@cmpxchg.org, guro@fb.com Subject: + mm-memcontrol-flush-percpu-vmstats-before-releasing-memcg.patch added to -mm tree Message-ID: <20190819222858.VDmEO%akpm@linux-foundation.org> User-Agent: s-nail v14.9.11 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm: memcontrol: flush percpu vmstats before releasing memcg has been added to the -mm tree. Its filename is mm-memcontrol-flush-percpu-vmstats-before-releasing-memcg.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-flush-percpu-vmstats-before-releasing-memcg.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-flush-percpu-vmstats-before-releasing-memcg.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Roman Gushchin Subject: mm: memcontrol: flush percpu vmstats before releasing memcg Percpu caching of local vmstats with the conditional propagation by the cgroup tree leads to an accumulation of errors on non-leaf levels. Let's imagine two nested memory cgroups A and A/B. Say, a process belonging to A/B allocates 100 pagecache pages on the CPU 0. The percpu cache will spill 3 times, so that 32*3=96 pages will be accounted to A/B and A atomic vmstat counters, 4 pages will remain in the percpu cache. Imagine A/B is nearby memory.max, so that every following allocation triggers a direct reclaim on the local CPU. Say, each such attempt will free 16 pages on a new cpu. That means every percpu cache will have -16 pages, except the first one, which will have 4 - 16 = -12. A/B and A atomic counters will not be touched at all. Now a user removes A/B. All percpu caches are freed and corresponding vmstat numbers are forgotten. A has 96 pages more than expected. As memory cgroups are created and destroyed, errors do accumulate. Even 1-2 pages differences can accumulate into large numbers. To fix this issue let's accumulate and propagate percpu vmstat values before releasing the memory cgroup. At this point these numbers are stable and cannot be changed. Since on cpu hotplug we do flush percpu vmstats anyway, we can iterate only over online cpus. Link: http://lkml.kernel.org/r/20190819202338.363363-2-guro@fb.com Fixes: 42a300353577 ("mm: memcontrol: fix recursive statistics correctness & scalabilty") Signed-off-by: Roman Gushchin Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Signed-off-by: Andrew Morton --- mm/memcontrol.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) --- a/mm/memcontrol.c~mm-memcontrol-flush-percpu-vmstats-before-releasing-memcg +++ a/mm/memcontrol.c @@ -3260,6 +3260,41 @@ static u64 mem_cgroup_read_u64(struct cg } } +static void memcg_flush_percpu_vmstats(struct mem_cgroup *memcg) +{ + unsigned long stat[MEMCG_NR_STAT]; + struct mem_cgroup *mi; + int node, cpu, i; + + for (i = 0; i < MEMCG_NR_STAT; i++) + stat[i] = 0; + + for_each_online_cpu(cpu) + for (i = 0; i < MEMCG_NR_STAT; i++) + stat[i] += raw_cpu_read(memcg->vmstats_percpu->stat[i]); + + for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) + for (i = 0; i < MEMCG_NR_STAT; i++) + atomic_long_add(stat[i], &mi->vmstats[i]); + + for_each_node(node) { + struct mem_cgroup_per_node *pn = memcg->nodeinfo[node]; + struct mem_cgroup_per_node *pi; + + for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) + stat[i] = 0; + + for_each_online_cpu(cpu) + for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) + stat[i] += raw_cpu_read( + pn->lruvec_stat_cpu->count[i]); + + for (pi = pn; pi; pi = parent_nodeinfo(pi, node)) + for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) + atomic_long_add(stat[i], &pi->lruvec_stat[i]); + } +} + #ifdef CONFIG_MEMCG_KMEM static int memcg_online_kmem(struct mem_cgroup *memcg) { @@ -4682,6 +4717,11 @@ static void __mem_cgroup_free(struct mem { int node; + /* + * Flush percpu vmstats to guarantee the value correctness + * on parent's and all ancestor levels. + */ + memcg_flush_percpu_vmstats(memcg); for_each_node(node) free_mem_cgroup_per_node_info(memcg, node); free_percpu(memcg->vmstats_percpu); _ Patches currently in -mm which might be from guro@fb.com are mm-memcontrol-flush-percpu-vmstats-before-releasing-memcg.patch mm-memcontrol-flush-percpu-slab-vmstats-on-kmem-offlining.patch mm-memcontrol-flush-percpu-vmevents-before-releasing-memcg.patch mm-memcontrol-switch-to-rcu-protection-in-drain_all_stock.patch