From nobody Sun Feb 8 01:30:08 2026 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70B6E1F4CB3 for ; Wed, 14 May 2025 05:08:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.184 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747199322; cv=none; b=Ye/WWCKvDdiYSM+WmWMq9PWqibkM8MLI74WrIVNuaS7i5agUykbhw9TB7QqfpqTilRvt1OLJ1xLI7EX/bZli//XU9AjjzJQwrfZgt6u9qY7evzU8fcym0xIc/PSLUouqS4o8LcvLDPpUw7Vr9ujqN+DIwxip8pm8AMGp04s7OLE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747199322; c=relaxed/simple; bh=8jpCKcYevABsM1E+ovY62bcN7h6ecmAAnFb2kM2PaZY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jGqLaExHfsfwxLQzFCfYjuobA+SLB+GmcJuNIUjEIlmKe9IWqPaVdWC/e8UyuSqYpNyIlO/uaEzdIggez/qWNbB6KO/mkf/ZmFCvfZ17Sp8Pyv7l5gvvGKlSbcDV37jHHsiPe+GAnN5xpn80KTrijlf5YY83fk6pbD8SmSpJxKg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Ufan84iQ; arc=none smtp.client-ip=91.218.175.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Ufan84iQ" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1747199317; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lT1lWRIc39oQfhab/AvhtsB7gjFHkHKvP88N+9WuUp8=; b=Ufan84iQx4kZ6ny1kDkEoY8jcItoUy+lGSmiHmEWOC/vnxckDXJ8pN7FdgVYDVZtg8IOYP WwRCYapOwVegFLk0yijnYzo88XArgShFZK0r+JpUQyd24hpzeJ9fo5Y9u7BOR4rGgJOjDR Otlz62CicA3jypXQ1jSx2lqykI4LCkk= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Vlastimil Babka , Alexei Starovoitov , Sebastian Andrzej Siewior , Harry Yoo , Yosry Ahmed , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: [PATCH 2/7] memcg: move preempt disable to callers of memcg_rstat_updated Date: Tue, 13 May 2025 22:08:08 -0700 Message-ID: <20250514050813.2526843-3-shakeel.butt@linux.dev> In-Reply-To: <20250514050813.2526843-1-shakeel.butt@linux.dev> References: <20250514050813.2526843-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" Let's move the explicit preempt disable code to the callers of memcg_rstat_updated and also remove the memcg_stats_lock and related functions which ensures the callers of stats update functions have disabled preemption because now the stats update functions are explicitly disabling preemption. Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka --- mm/memcontrol.c | 74 +++++++++++++------------------------------------ 1 file changed, 19 insertions(+), 55 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index cb10bcd1028d..8c8e0e1acd71 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -558,47 +558,21 @@ static u64 flush_last_time; =20 #define FLUSH_TIME (2UL*HZ) =20 -/* - * Accessors to ensure that preemption is disabled on PREEMPT_RT because i= t can - * not rely on this as part of an acquired spinlock_t lock. These function= s are - * never used in hardirq context on PREEMPT_RT and therefore disabling pre= emtion - * is sufficient. - */ -static void memcg_stats_lock(void) -{ - preempt_disable_nested(); - VM_WARN_ON_IRQS_ENABLED(); -} - -static void __memcg_stats_lock(void) -{ - preempt_disable_nested(); -} - -static void memcg_stats_unlock(void) -{ - preempt_enable_nested(); -} - - static bool memcg_vmstats_needs_flush(struct memcg_vmstats *vmstats) { return atomic64_read(&vmstats->stats_updates) > MEMCG_CHARGE_BATCH * num_online_cpus(); } =20 -static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val) +static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val, + int cpu) { struct memcg_vmstats_percpu __percpu *statc_pcpu; - int cpu; unsigned int stats_updates; =20 if (!val) return; =20 - /* Don't assume callers have preemption disabled. */ - cpu =3D get_cpu(); - css_rstat_updated(&memcg->css, cpu); statc_pcpu =3D memcg->vmstats_percpu; for (; statc_pcpu; statc_pcpu =3D this_cpu_ptr(statc_pcpu)->parent_pcpu) { @@ -620,7 +594,6 @@ static inline void memcg_rstat_updated(struct mem_cgrou= p *memcg, int val) atomic64_add(stats_updates, &this_cpu_ptr(statc_pcpu)->vmstats->stats_updates); } - put_cpu(); } =20 static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force) @@ -718,6 +691,7 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum m= emcg_stat_item idx, int val) { int i =3D memcg_stats_index(idx); + int cpu; =20 if (mem_cgroup_disabled()) return; @@ -725,12 +699,14 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum= memcg_stat_item idx, if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, id= x)) return; =20 - memcg_stats_lock(); + cpu =3D get_cpu(); + __this_cpu_add(memcg->vmstats_percpu->state[i], val); val =3D memcg_state_val_in_pages(idx, val); - memcg_rstat_updated(memcg, val); + memcg_rstat_updated(memcg, val, cpu); trace_mod_memcg_state(memcg, idx, val); - memcg_stats_unlock(); + + put_cpu(); } =20 #ifdef CONFIG_MEMCG_V1 @@ -759,6 +735,7 @@ static void __mod_memcg_lruvec_state(struct lruvec *lru= vec, struct mem_cgroup_per_node *pn; struct mem_cgroup *memcg; int i =3D memcg_stats_index(idx); + int cpu; =20 if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, id= x)) return; @@ -766,24 +743,7 @@ static void __mod_memcg_lruvec_state(struct lruvec *lr= uvec, pn =3D container_of(lruvec, struct mem_cgroup_per_node, lruvec); memcg =3D pn->memcg; =20 - /* - * The caller from rmap relies on disabled preemption because they never - * update their counter from in-interrupt context. For these two - * counters we check that the update is never performed from an - * interrupt context while other caller need to have disabled interrupt. - */ - __memcg_stats_lock(); - if (IS_ENABLED(CONFIG_DEBUG_VM)) { - switch (idx) { - case NR_ANON_MAPPED: - case NR_FILE_MAPPED: - case NR_ANON_THPS: - WARN_ON_ONCE(!in_task()); - break; - default: - VM_WARN_ON_IRQS_ENABLED(); - } - } + cpu =3D get_cpu(); =20 /* Update memcg */ __this_cpu_add(memcg->vmstats_percpu->state[i], val); @@ -792,9 +752,10 @@ static void __mod_memcg_lruvec_state(struct lruvec *lr= uvec, __this_cpu_add(pn->lruvec_stats_percpu->state[i], val); =20 val =3D memcg_state_val_in_pages(idx, val); - memcg_rstat_updated(memcg, val); + memcg_rstat_updated(memcg, val, cpu); trace_mod_memcg_lruvec_state(memcg, idx, val); - memcg_stats_unlock(); + + put_cpu(); } =20 /** @@ -874,6 +835,7 @@ void __count_memcg_events(struct mem_cgroup *memcg, enu= m vm_event_item idx, unsigned long count) { int i =3D memcg_events_index(idx); + int cpu; =20 if (mem_cgroup_disabled()) return; @@ -881,11 +843,13 @@ void __count_memcg_events(struct mem_cgroup *memcg, e= num vm_event_item idx, if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, id= x)) return; =20 - memcg_stats_lock(); + cpu =3D get_cpu(); + __this_cpu_add(memcg->vmstats_percpu->events[i], count); - memcg_rstat_updated(memcg, count); + memcg_rstat_updated(memcg, count, cpu); trace_count_memcg_events(memcg, idx, count); - memcg_stats_unlock(); + + put_cpu(); } =20 unsigned long memcg_events(struct mem_cgroup *memcg, int event) --=20 2.47.1