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Fri, 16 Dec 2022 16:52:10 -0300 (-03) Message-ID: <20221216194904.272106293@redhat.com> User-Agent: quilt/0.66 Date: Fri, 16 Dec 2022 16:45:46 -0300 From: Marcelo Tosatti To: atomlin@redhat.com, frederic@kernel.org Cc: cl@linux.com, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Marcelo Tosatti Subject: [PATCH v10 6/6] mm/vmstat: avoid queueing work item if cpu stats are clean References: <20221216194540.202752779@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspam-User: X-Rspamd-Queue-Id: 3F5E420004 X-Rspamd-Server: rspam01 X-Stat-Signature: a7ntb1ypb1u5swo73rdo5ywoia47in3w X-HE-Tag: 1671220363-748800 X-HE-Meta: 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 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: It is not necessary to queue work item to run refresh_vm_stats on a remote CPU if that CPU has no dirty stats and no per-CPU allocations for remote nodes. This fixes sosreport hang (which uses vmstat_refresh) with spinning SCHED_FIFO process. Signed-off-by: Marcelo Tosatti Index: linux-2.6/mm/vmstat.c =================================================================== --- linux-2.6.orig/mm/vmstat.c +++ linux-2.6/mm/vmstat.c @@ -1905,6 +1905,31 @@ static const struct seq_operations vmsta #ifdef CONFIG_SMP #ifdef CONFIG_PROC_FS +static bool need_drain_remote_zones(int cpu) +{ +#ifdef CONFIG_NUMA + struct zone *zone; + + for_each_populated_zone(zone) { + struct per_cpu_pages *pcp; + + pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); + if (!pcp->count) + continue; + + if (!pcp->expire) + continue; + + if (zone_to_nid(zone) == cpu_to_node(cpu)) + continue; + + return true; + } +#endif + + return false; +} + static void refresh_vm_stats(struct work_struct *work) { refresh_cpu_vm_stats(true); @@ -1914,8 +1939,12 @@ int vmstat_refresh(struct ctl_table *tab void *buffer, size_t *lenp, loff_t *ppos) { long val; - int err; - int i; + int i, cpu; + struct work_struct __percpu *works; + + works = alloc_percpu(struct work_struct); + if (!works) + return -ENOMEM; /* * The regular update, every sysctl_stat_interval, may come later @@ -1929,9 +1958,19 @@ int vmstat_refresh(struct ctl_table *tab * transiently negative values, report an error here if any of * the stats is negative, so we know to go looking for imbalance. */ - err = schedule_on_each_cpu(refresh_vm_stats); - if (err) - return err; + cpus_read_lock(); + for_each_online_cpu(cpu) { + struct work_struct *work = per_cpu_ptr(works, cpu); + + INIT_WORK(work, refresh_vm_stats); + if (per_cpu(vmstat_dirty, cpu) || need_drain_remote_zones(cpu)) + schedule_work_on(cpu, work); + } + for_each_online_cpu(cpu) + flush_work(per_cpu_ptr(works, cpu)); + cpus_read_unlock(); + free_percpu(works); + for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) { /* * Skip checking stats known to go negative occasionally.