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=-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=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 C70DCC4167D for ; Thu, 2 Sep 2021 21:55:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE8156112F for ; Thu, 2 Sep 2021 21:55:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347780AbhIBV4F (ORCPT ); Thu, 2 Sep 2021 17:56:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:50482 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347866AbhIBV4D (ORCPT ); Thu, 2 Sep 2021 17:56:03 -0400 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 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org =46rom: 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.=20 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 Koutn=C3=BD Cc: Muchun Song Cc: Roman Gushchin Cc: Tejun Heo Signed-off-by: Andrew Morton --- 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; } =20 +void mem_cgroup_flush_stats(void); + void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item i= dx, 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); } =20 +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; } =20 +/* 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 =20 @@ -674,6 +682,8 @@ void __mod_memcg_lruvec_state(struct lru =20 /* 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); } =20 /** @@ -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; } =20 @@ -5331,6 +5345,26 @@ static void mem_cgroup_css_reset(struct memcg_wb_domain_size_changed(memcg); } =20 +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, in= t cpu) { struct mem_cgroup *memcg =3D 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 =3D mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); =20 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)); =20 nr_reclaimed =3D sc->nr_reclaimed; _