Messages in this thread Patch in this message | | | Date | Wed, 14 Jul 2021 17:42:10 -0300 | From | Marcelo Tosatti <> | Subject | [patch 5/5] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean |
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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 <mtosatti@redhat.com>
Index: linux-2.6-vmstat-update/mm/vmstat.c =================================================================== --- linux-2.6-vmstat-update.orig/mm/vmstat.c +++ linux-2.6-vmstat-update/mm/vmstat.c @@ -1888,17 +1888,41 @@ static bool need_update(int cpu) } #ifdef CONFIG_PROC_FS -static void refresh_vm_stats(struct work_struct *work) +static bool need_drain_remote_zones(int cpu) +{ + struct zone *zone; + + for_each_populated_zone(zone) { + struct per_cpu_pageset *p; + + p = per_cpu_ptr(zone->pageset, cpu); + + if (!p->pcp.count) + continue; +#ifdef CONFIG_NUMA + if (!p->expire) + continue; +#endif + if (zone_to_nid(zone) == cpu_to_node(cpu)) + continue; + + return true; + } + + return false; +} + +static long refresh_vm_stats(void *arg) { refresh_cpu_vm_stats(true); + return 0; } int vmstat_refresh(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { long val; - int err; - int i; + int i, cpu; /* * The regular update, every sysctl_stat_interval, may come later @@ -1912,9 +1936,15 @@ 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; + get_online_cpus(); + for_each_online_cpu(cpu) { + if (need_update(cpu) || need_drain_remote_zones(cpu)) + work_on_cpu(cpu, refresh_vm_stats, NULL); + + cond_resched(); + } + put_online_cpus(); + for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) { /* * Skip checking stats known to go negative occasionally.
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