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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1747106028; 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=/8sFVhv+XawDkwe/3YGMSQXN4zaIyJz49c278HEHQGA=; b=C3EQVIw8Y1nTVChBcJCKWIBxYqV4/Y1lz/1Ujxcqedmdus/MZqYNUvrgok9fdfCOPb626J esIQ4xLECOxawcCDqHWReJVu3iDYZQmbVGRspPyxWAJtsTt0J07twE74pSmbLhyaf4m8YA KuJRH8xcc9tkRoSw146PCOltrl4otFI= 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: [RFC PATCH 2/7] memcg: move preempt disable to callers of memcg_rstat_updated Date: Mon, 12 May 2025 20:13:11 -0700 Message-ID: <20250513031316.2147548-3-shakeel.butt@linux.dev> In-Reply-To: <20250513031316.2147548-1-shakeel.butt@linux.dev> References: <20250513031316.2147548-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 6964C1A0005 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: qmcuwznqmbk5tzyhu8f1au57ms89cqar X-HE-Tag: 1747106031-201731 X-HE-Meta: U2FsdGVkX19UsJFPyrzBx8bcNvZsCbUoUkg6fHjB20brww/V4la4l8R4Tcj+PoO4pMfFtMjR1/WCL0iAWHyqotaZxZjwki/nOmVD10wsIU/+6POCyp6ule/lgAe5XRkQrKbUpKaPLtS6pAPQTFo1m5FpwNBRx35VyPMhchDEbYoabRLHau4ZLRn7Jl38fH0Z5w/FgRXYApOzhPfI3eiIzNgq27sSKl4AV4nK2Pxh6H9tPpt42eSR3I+G2vlbWLF+QYcQDKHTFPONTlk0J1yujXkGB+pebZSFZPoVRMj5VVWqfYa9jn8Auf2ThQm+pIKKbBYW7FSbhYkS+mcHluacGKwOE5CBWYmAJP3D8hjA+lFE41swBwoX3BdMmh33oV5NvzOfiRTQNhAis8FD33CTAdKzJX0Ot2q2TiGI/ml/ztAfha8P7Z+0qpR1exgt58x+E8aRyobJt6LdjLpUlqWZv3C9ZwQ+MAc4ZaUJ038OqP+VPdcAzjZZMY1ldv28IS4xtN5TDPmU/GwbdnFCWWwvNieO9MOW+3DgZTrWeEV00JUI9QzHYZTgDApFd/Qz9HEWHR49ungTjPLnJFYzvXHc0E8iTgopbv046Jf734jKtbnolgfWFT1wZhiFWkW87qlcS6OQsvtcd0sDhQ+SSnK52bF8IhkHhEZZh2jaLMcMV+T+tnCzbran3qUWjnZ3PrWb70CV+Sjt3oqcUyku+eReu2Ldo9KwGc5mO4CM2YjHcwGAInjMLYHMAWqwMkeW+41d8HWW2Dt0Qi/h2pX36i6ic20c/TE3iN64mYkQnCj3naxI5SK7hlzW+7crGT8YCPrfMalf7U9G/h7YsCByZ6YyS0V3QPHKL1l6premjzLYk2hZNs8C2B2mhFFnoZyxw6zhEFC0PPBkwUZFEnGAfS7au5kKM8clxt0V1gf5ERaDGsxY2m3Dc3jbJNm09akZqVLQXOFFGTwm4IcKyXK4aP/ N0mfkKBq 2imopQdXnimhxZky/T75KKL4h102Ltp/T11MLaKELh0I3I/rC85wEvQfY+zs5UqWEK9mhRL4zm5tQgIUQlbfJ8YBfYg9coIwgfbWLXoH/j0B7d4LnZs+9im35hbR49DPQNIURhE1relLkzt/yGRqhEDHjrwtRE3hl7WsnqMt0nfaRe4EgZ51ktewbp93qcitSWRufWuYAumcnFjkMBhbg4ijqwrXAlXG9Q0yq 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: List-Subscribe: List-Unsubscribe: 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 --- mm/memcontrol.c | 74 +++++++++++++------------------------------------ 1 file changed, 19 insertions(+), 55 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2c4c095bf26c..62450e7991d8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -558,47 +558,21 @@ static u64 flush_last_time; #define FLUSH_TIME (2UL*HZ) -/* - * Accessors to ensure that preemption is disabled on PREEMPT_RT because it can - * not rely on this as part of an acquired spinlock_t lock. These functions are - * never used in hardirq context on PREEMPT_RT and therefore disabling preemtion - * 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(); } -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 *statc; - int cpu; int stats_updates; if (!val) return; - /* Don't assume callers have preemption disabled. */ - cpu = get_cpu(); - cgroup_rstat_updated(memcg->css.cgroup, cpu); statc = this_cpu_ptr(memcg->vmstats_percpu); for (; statc; statc = statc->parent) { @@ -619,7 +593,6 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val) atomic64_add(stats_updates, &statc->vmstats->stats_updates); } - put_cpu(); } static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force) @@ -717,6 +690,7 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx, int val) { int i = memcg_stats_index(idx); + int cpu; if (mem_cgroup_disabled()) return; @@ -724,12 +698,14 @@ 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__, idx)) return; - memcg_stats_lock(); + cpu = get_cpu(); + __this_cpu_add(memcg->vmstats_percpu->state[i], val); val = 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(); } #ifdef CONFIG_MEMCG_V1 @@ -758,6 +734,7 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec, struct mem_cgroup_per_node *pn; struct mem_cgroup *memcg; int i = memcg_stats_index(idx); + int cpu; if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx)) return; @@ -765,24 +742,7 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec, pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); memcg = pn->memcg; - /* - * 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 = get_cpu(); /* Update memcg */ __this_cpu_add(memcg->vmstats_percpu->state[i], val); @@ -791,9 +751,10 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec, __this_cpu_add(pn->lruvec_stats_percpu->state[i], val); val = 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(); } /** @@ -873,6 +834,7 @@ void __count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx, unsigned long count) { int i = memcg_events_index(idx); + int cpu; if (mem_cgroup_disabled()) return; @@ -880,11 +842,13 @@ void __count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx, if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx)) return; - memcg_stats_lock(); + cpu = 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(); } unsigned long memcg_events(struct mem_cgroup *memcg, int event) -- 2.47.1