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=-6.8 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,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 B403DC3A5A3 for ; Tue, 27 Aug 2019 08:07:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8587B2189D for ; Tue, 27 Aug 2019 08:07:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566893247; bh=5l8NdeJXT/Pd1cRyEEteliHe12VXiLgTXUaRCo6yo38=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xo0UjX2frzWLBOqtrnptqRhYNz0ge5ddfNgl/hZiNsTdeNMqxLT5YxpPVSH9AjvTg q5/rCKPp37U4RUaw3VhGuRDPUWfnZVTeGHM77lTpCDLNILEaxtaoZORU/hxKTtElyW vr19tfk0aQ+GiyFtVMriIR5LTC+f5/CHJCSkOkmc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732911AbfH0IH0 (ORCPT ); Tue, 27 Aug 2019 04:07:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:37448 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730471AbfH0IHY (ORCPT ); Tue, 27 Aug 2019 04:07:24 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 C1B8D206BA; Tue, 27 Aug 2019 08:07:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566893243; bh=5l8NdeJXT/Pd1cRyEEteliHe12VXiLgTXUaRCo6yo38=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mgyPoAFWWjRctR9q/WL5HUAJHoQospiQHQriJ+/Rol7hmdx98nO6eZ7oGwC2snZXG vjUQheSJnVb+Cxsz6cR6oqBvHJEQ+J5d9z4fieMh3+4fvK1K79bm2EiVBk/b9zt78l Rz2KgPRlo6LLnxLO0o0LYwHwh6o47DlZwVOLjHT0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Roman Gushchin , Michal Hocko , Johannes Weiner , Vladimir Davydov , Andrew Morton , Linus Torvalds Subject: [PATCH 5.2 148/162] mm: memcontrol: flush percpu vmstats before releasing memcg Date: Tue, 27 Aug 2019 09:51:16 +0200 Message-Id: <20190827072743.890460259@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190827072738.093683223@linuxfoundation.org> References: <20190827072738.093683223@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Roman Gushchin commit c350a99ea2b1b666c28948d74ab46c16913c28a7 upstream. 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 Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memcontrol.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3150,6 +3150,41 @@ 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) { @@ -4551,6 +4586,11 @@ 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);