From patchwork Thu Sep 2 21:55:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12473023 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 9734DC00306 for ; Thu, 2 Sep 2021 21:55:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4863B610D2 for ; Thu, 2 Sep 2021 21:55:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 4863B610D2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id EBA806B00E7; Thu, 2 Sep 2021 17:55:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E69EB6B00E8; Thu, 2 Sep 2021 17:55:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D59858D0001; Thu, 2 Sep 2021 17:55:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0076.hostedemail.com [216.40.44.76]) by kanga.kvack.org (Postfix) with ESMTP id C54CE6B00E7 for ; Thu, 2 Sep 2021 17:55:07 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 8A38A85F19AD for ; Thu, 2 Sep 2021 21:55:07 +0000 (UTC) X-FDA: 78543989454.05.8A05B3D Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf22.hostedemail.com (Postfix) with ESMTP id 2AA541901 for ; Thu, 2 Sep 2021 21:55:07 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 82673610CF; Thu, 2 Sep 2021 21:55:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1630619704; bh=Ylv4FO6aBTEysbgu/+K2p5GLG9ehe6J2lFw/zNetmoQ=; h=Date:From:To:Subject:In-Reply-To:From; b=Z6rnCzENg7IF1gifJx9CbhGi8wRPt7QL80m4gROnCrmerwM2/fNFOZUbBD/uV/pGj Bza3noR5TrW3iaIN/KnL8B6OZpf7/mhvTDfQ9WAzgRRdQfzi8Qm3ZPEwYGtjtNRY/f ZvZQ9PbdDF86MNHJu5T78alkKDESW8DaTKKrjMEI= Date: Thu, 02 Sep 2021 14:55:04 -0700 From: Andrew Morton To: akpm@linux-foundation.org, guro@fb.com, hannes@cmpxchg.org, hdanton@sina.com, linux-mm@kvack.org, m.szyprowski@samsung.com, mhocko@kernel.org, mkoutny@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, songmuchun@bytedance.com, tj@kernel.org, torvalds@linux-foundation.org, ying.huang@intel.com Subject: [patch 097/212] memcg: infrastructure to flush memcg stats Message-ID: <20210902215504.dSSfDKJZu%akpm@linux-foundation.org> In-Reply-To: <20210902144820.78957dff93d7bea620d55a89@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=Z6rnCzEN; spf=pass (imf22.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2AA541901 X-Stat-Signature: a54o43aegprg6453a6wpf8ujafj8cdqe X-HE-Tag: 1630619707-784795 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: From: Shakeel Butt Subject: memcg: infrastructure to flush memcg stats 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. However we would have to use irqsafe version of rstat flush but that is fine as this code path will be flushing for whole tree and do the work for everyone. No one will be waiting for that worker. [shakeelb@google.com: fix sleep-in-wrong context bug] Link: https://lkml.kernel.org/r/20210716212137.1391164-2-shakeelb@google.com Link: https://lkml.kernel.org/r/20210714013948.270662-2-shakeelb@google.com Signed-off-by: Shakeel Butt Tested-by: Marek Szyprowski Cc: Hillf Danton Cc: Huang Ying Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Koutný Cc: Muchun Song Cc: Roman Gushchin Cc: Tejun Heo Signed-off-by: Andrew Morton Reported-by: kernel test robot --- include/linux/memcontrol.h | 6 ++++++ mm/memcontrol.c | 34 ++++++++++++++++++++++++++++++++++ mm/vmscan.c | 6 ++++++ 3 files changed, 46 insertions(+) --- a/include/linux/memcontrol.h~memcg-infrastructure-to-flush-memcg-stats +++ a/include/linux/memcontrol.h @@ -1023,6 +1023,8 @@ static inline unsigned long lruvec_page_ 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); @@ -1438,6 +1440,10 @@ static inline unsigned long lruvec_page_ 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) { --- a/mm/memcontrol.c~memcg-infrastructure-to-flush-memcg-stats +++ a/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 @@ -674,6 +682,8 @@ void __mod_memcg_lruvec_state(struct lru /* 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); } /** @@ -5240,6 +5250,10 @@ static int mem_cgroup_css_online(struct /* 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; } @@ -5331,6 +5345,26 @@ static void mem_cgroup_css_reset(struct memcg_wb_domain_size_changed(memcg); } +void mem_cgroup_flush_stats(void) +{ + if (!spin_trylock(&stats_flush_lock)) + return; + + cgroup_rstat_flush_irqsafe(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); --- a/mm/vmscan.c~memcg-infrastructure-to-flush-memcg-stats +++ a/mm/vmscan.c @@ -2897,6 +2897,12 @@ static void shrink_node(pg_data_t *pgdat 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;