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=-21.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL 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 6FEF1C11F67 for ; Tue, 13 Jul 2021 20:24:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DE2061369 for ; Tue, 13 Jul 2021 20:24:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235572AbhGMU1M (ORCPT ); Tue, 13 Jul 2021 16:27:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235413AbhGMU1L (ORCPT ); Tue, 13 Jul 2021 16:27:11 -0400 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [IPv6:2607:f8b0:4864:20::1049]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4586FC0613EF for ; Tue, 13 Jul 2021 13:24:21 -0700 (PDT) Received: by mail-pj1-x1049.google.com with SMTP id k23-20020a17090a5917b02901739510b17fso5004720pji.6 for ; Tue, 13 Jul 2021 13:24:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=EHAYE05GAu+niMbde+c2BkAYKkWBFNQ1NKRMcAVAVMc=; b=gKeP0lrlLzavl+bP2FEXh/IMOv/on+DOO4SjIuZd90lujGClYWiPwVADRjnqM6k4rL VUdsQJeumADj1m9LGp5Kb+Vgd1H8iFqcTZjsVOUDQ5e4PPf7bET8MCIOGQhMiyyaNm3X mdTHi7e0RJQ3gvmuWttCxxw9rfydRGVRrObaNXXYipMVOUlUldWoCgaXawR4RpU5uYZ1 sPyayHFWIth2GWlSa8CSPGgj83LtxlEG8em/J7DD/6RJL9K0eMVPM70QUVzBFimfvu6d 7KCHAomuOwUbrVoZ81kD/VN8s014fjFRhpGPkWmDe25p3XhCrRIuf0R1sdFj1nL3gqWq cN+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=EHAYE05GAu+niMbde+c2BkAYKkWBFNQ1NKRMcAVAVMc=; b=cAb4iVgkgMpzSMiyokG8qJHaeOrGnVxGP7zjW6yIhrvl01KVw1H2kxLkGU8KPrPk9/ y74OgVFjCKzuotMeS7tqL3qss8q1JDjh7PhKHuiFk6k0GwyLfMnvYuGCAox5TBDzQZvb XodK1NPCztgK3FHqghPRUWTFrbDSvPizo/BoIF1xTypSEIK8stGcObtZ5PJ3gz/Yo0YW eMUIVW7nmLibyzpk0k37iK8AuFHJIHsBrwiDz6bhcQ7weT3gIZhiu3F3vk44X79AaNU1 pSvysSNXzzONqVrUtVtzqxeWZO6ooyBB9deRezA/eOhWuWf1NUiFSZ/Rl3tZYfnrf4rB PNzw== X-Gm-Message-State: AOAM531KpohLJS2wyG2t6LNp8Vy4Wb+2NTqhkn0E7OsAPk0sf23+kayf KZSIrAwMXlIjbUzmH72hJpbcbUyxFHjm6w== X-Google-Smtp-Source: ABdhPJxRmtyeKKnYhuV8eHDTnOI9kWYJGdkl7JZyqqiCjCELzK2xCP+sct+v8gi5+aV00J+f8BFa46imiHijYg== X-Received: from shakeelb.svl.corp.google.com ([2620:15c:2cd:202:c6c:5381:cc6a:6baa]) (user=shakeelb job=sendgmr) by 2002:a17:90b:347:: with SMTP id fh7mr47998pjb.2.1626207860793; Tue, 13 Jul 2021 13:24:20 -0700 (PDT) Date: Tue, 13 Jul 2021 13:24:12 -0700 In-Reply-To: <20210713202412.248252-1-shakeelb@google.com> Message-Id: <20210713202412.248252-2-shakeelb@google.com> Mime-Version: 1.0 References: <20210713202412.248252-1-shakeelb@google.com> X-Mailer: git-send-email 2.32.0.93.g670b81a890-goog Subject: [PATCH 2/2] memcg: infrastructure to flush memcg stats From: Shakeel Butt To: Tejun Heo , Johannes Weiner , Muchun Song Cc: Michal Hocko , Roman Gushchin , "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , Huang Ying , Hillf Danton , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At the moment memcg stats are read in four contexts: 1. memcg stat user interfaces 2. dirty throttling 3. page fault 4. memory reclaim Currently the kernel flushes the stats for first two cases. Flushing the stats for remaining two casese may have performance impact. Always flushing the memcg stats on the page fault code path may negatively impacts the performance of the applications. In addition flushing in the memory reclaim code path, though treated as slowpath, can become the source of contention for the global lock taken for stat flushing because when system or memcg is under memory pressure, many tasks may enter the reclaim path. This patch uses following mechanisms to solve these challenges: 1. Periodically flush the stats from root memcg every 2 seconds. This will time limit the out of sync stats. 2. Asynchronously flush the stats after fixed number of stat updates. In the worst case the stat can be out of sync by O(nr_cpus * BATCH) for 2 seconds. 3. For avoiding thundering herd to flush the stats particularly from the memory reclaim context, introduce memcg local spinlock and let only one flusher active at a time. This could have been done through cgroup_rstat_lock lock but that lock is used by other subsystem and for userspace reading memcg stats. So, it is better to keep flushers introduced by this patch decoupled from cgroup_rstat_lock. --- Changes since v2: - Changed the subject of the patch - Added mechanism to bound errors to nr_cpus instead of nr_cgroups - memcg local lock to let one active flusher Changes since v1: - use system_unbound_wq for flushing the memcg stats include/linux/memcontrol.h | 6 ++++++ mm/memcontrol.c | 34 ++++++++++++++++++++++++++++++++++ mm/vmscan.c | 6 ++++++ 3 files changed, 46 insertions(+) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 0bfa0409af22..fa095a94ae56 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -991,6 +991,8 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, return x; } +void mem_cgroup_flush_stats(void); + void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, int val); void __mod_lruvec_kmem_state(void *p, enum node_stat_item idx, int val); @@ -1400,6 +1402,10 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, return node_page_state(lruvec_pgdat(lruvec), idx); } +static inline void mem_cgroup_flush_stats(void) +{ +} + static inline void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, int val) { diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 848d711bf576..39a00991fc80 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -103,6 +103,14 @@ static bool do_memsw_account(void) return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap; } +/* memcg and lruvec stats flushing */ +static void flush_memcg_stats_dwork(struct work_struct *w); +static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork); +static void flush_memcg_stats_work(struct work_struct *w); +static DECLARE_WORK(stats_flush_work, flush_memcg_stats_work); +static DEFINE_PER_CPU(unsigned int, stats_flush_threshold); +static DEFINE_SPINLOCK(stats_flush_lock); + #define THRESHOLDS_EVENTS_TARGET 128 #define SOFTLIMIT_EVENTS_TARGET 1024 @@ -685,6 +693,8 @@ void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, /* Update lruvec */ __this_cpu_add(pn->lruvec_stats_percpu->state[idx], val); + if (!(__this_cpu_inc_return(stats_flush_threshold) % MEMCG_CHARGE_BATCH)) + queue_work(system_unbound_wq, &stats_flush_work); } /** @@ -5248,6 +5258,10 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) /* Online state pins memcg ID, memcg ID pins CSS */ refcount_set(&memcg->id.ref, 1); css_get(css); + + if (unlikely(mem_cgroup_is_root(memcg))) + queue_delayed_work(system_unbound_wq, &stats_flush_dwork, + 2UL*HZ); return 0; } @@ -5339,6 +5353,26 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css) memcg_wb_domain_size_changed(memcg); } +void mem_cgroup_flush_stats(void) +{ + if (!spin_trylock(&stats_flush_lock)) + return; + + cgroup_rstat_flush(root_mem_cgroup->css.cgroup); + spin_unlock(&stats_flush_lock); +} + +static void flush_memcg_stats_dwork(struct work_struct *w) +{ + mem_cgroup_flush_stats(); + queue_delayed_work(system_unbound_wq, &stats_flush_dwork, 2UL*HZ); +} + +static void flush_memcg_stats_work(struct work_struct *w) +{ + mem_cgroup_flush_stats(); +} + static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) { struct mem_cgroup *memcg = mem_cgroup_from_css(css); diff --git a/mm/vmscan.c b/mm/vmscan.c index a7602f71ec04..1cc05ab8ca15 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2893,6 +2893,12 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); again: + /* + * Flush the memory cgroup stats, so that we read accurate per-memcg + * lruvec stats for heuristics. + */ + mem_cgroup_flush_stats(); + memset(&sc->nr, 0, sizeof(sc->nr)); nr_reclaimed = sc->nr_reclaimed; -- 2.32.0.93.g670b81a890-goog