From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta1.migadu.com (out-174.mta1.migadu.com [95.215.58.174]) (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 D1E0D27467D for ; Fri, 16 May 2025 18:33:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747420417; cv=none; b=cTnmRbzyOVLpvhcup4sEznUqr2UZN/M6DHb8RsxcT5qlWUBUEIlPJkPQSeUyNnKQk6CR4spnhACbNI2h5SOubhZng6v5Y1Z8wezgFmsJPXBB2EMbLtfe5QgLVQtMQbGIKURil7PiWTk++yoAJYmExIt1yi28D3mKnESKHolWy08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747420417; c=relaxed/simple; bh=L1FANs75GnyENPpCSObB44OAjAEmVoUmb9ZL9SNNgvw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PD0v8lNVroSKtGyt1NgT/hSgZ1JB2mMYpJr2rXbMCL4mVWyse4lyPYIyZ76dFoTrQEFyAK7+ugE/OTMfZEFRc0w8Ina6oTRIYAZjqt+/Y4IfIbbor5vTwTYGKqzarbyzk+KDwDKHjySJKC6J2fayX9zbLFE2GVaI/8v7C4ejtX4= 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=wGT+sTxw; arc=none smtp.client-ip=95.215.58.174 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="wGT+sTxw" 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=1747420413; 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=1SZJx0aaLO11/z+3A95G9xQwNAh1dQNdtZG0PH2m5B0=; b=wGT+sTxw8c5WygTZyHNWxHhaBeB2Db0T1IwGsnrjo6DRHxIVPalq/OKAbL348LKt8va1ok aKSVg6JumoxRhbeUydIJnLCYaUZl1g3qyRWzBYmuyhOu/Iqm6w+cA2tmqB2KV7rna+FWdP 5QoUGw+Hj0IkXGCzjaLre2twvGqg3tg= 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 , Peter Zijlstra , Mathieu Desnoyers , Tejun Heo , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: [PATCH v3 5/5] memcg: make memcg_rstat_updated nmi safe Date: Fri, 16 May 2025 11:32:31 -0700 Message-ID: <20250516183231.1615590-6-shakeel.butt@linux.dev> In-Reply-To: <20250516183231.1615590-1-shakeel.butt@linux.dev> References: <20250516183231.1615590-1-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: 8bit X-Migadu-Flow: FLOW_OUT Currently kernel maintains memory related stats updates per-cgroup to optimize stats flushing. The stats_updates is defined as atomic64_t which is not nmi-safe on some archs. Actually we don't really need 64bit atomic as the max value stats_updates can get should be less than nr_cpus * MEMCG_CHARGE_BATCH. A normal atomic_t should suffice. Also the function cgroup_rstat_updated() is still not nmi-safe but there is parallel effort to make it nmi-safe, so until then let's ignore it in the nmi context. Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka --- mm/memcontrol.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e96c5d1ca912..2ace30fcd0e6 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -533,7 +533,7 @@ struct memcg_vmstats { unsigned long events_pending[NR_MEMCG_EVENTS]; /* Stats updates since the last flush */ - atomic64_t stats_updates; + atomic_t stats_updates; }; /* @@ -559,7 +559,7 @@ static u64 flush_last_time; static bool memcg_vmstats_needs_flush(struct memcg_vmstats *vmstats) { - return atomic64_read(&vmstats->stats_updates) > + return atomic_read(&vmstats->stats_updates) > MEMCG_CHARGE_BATCH * num_online_cpus(); } @@ -573,7 +573,9 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val, if (!val) return; - cgroup_rstat_updated(memcg->css.cgroup, cpu); + /* TODO: add to cgroup update tree once it is nmi-safe. */ + if (!in_nmi()) + cgroup_rstat_updated(memcg->css.cgroup, cpu); statc_pcpu = memcg->vmstats_percpu; for (; statc_pcpu; statc_pcpu = statc->parent_pcpu) { statc = this_cpu_ptr(statc_pcpu); @@ -591,7 +593,7 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val, continue; stats_updates = this_cpu_xchg(statc_pcpu->stats_updates, 0); - atomic64_add(stats_updates, &statc->vmstats->stats_updates); + atomic_add(stats_updates, &statc->vmstats->stats_updates); } } @@ -599,7 +601,7 @@ static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force) { bool needs_flush = memcg_vmstats_needs_flush(memcg->vmstats); - trace_memcg_flush_stats(memcg, atomic64_read(&memcg->vmstats->stats_updates), + trace_memcg_flush_stats(memcg, atomic_read(&memcg->vmstats->stats_updates), force, needs_flush); if (!force && !needs_flush) @@ -4132,8 +4134,8 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) } WRITE_ONCE(statc->stats_updates, 0); /* We are in a per-cpu loop here, only do the atomic write once */ - if (atomic64_read(&memcg->vmstats->stats_updates)) - atomic64_set(&memcg->vmstats->stats_updates, 0); + if (atomic_read(&memcg->vmstats->stats_updates)) + atomic_set(&memcg->vmstats->stats_updates, 0); } static void mem_cgroup_fork(struct task_struct *task) -- 2.47.1