The interruption caused by queueing work on nohz_full CPUs
is undesirable for certain aplications.
Fix by not refreshing per-CPU stats of nohz_full CPUs.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
---
Index: linux-vmstat-remote/mm/vmstat.c
===================================================================
--- linux-vmstat-remote.orig/mm/vmstat.c
+++ linux-vmstat-remote/mm/vmstat.c
@@ -1877,12 +1877,31 @@ static void refresh_vm_stats(struct work
refresh_cpu_vm_stats(true);
}
+#ifdef CONFIG_NO_HZ_FULL
+static inline const cpumask_t *tickless_cpumask(void)
+{
+ return tick_nohz_full_mask;
+}
+#else
+static cpumask_t empty_cpumask;
+static inline const cpumask_t *tickless_cpumask(void)
+{
+ return &empty_cpumask;
+}
+#endif
+
int vmstat_refresh(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
long val;
int err;
int i;
+ cpumask_var_t dstmask;
+
+ if (!alloc_cpumask_var(&dstmask, GFP_KERNEL))
+ return -ENOMEM;
+
+ cpumask_andnot(dstmask, cpu_possible_mask, tickless_cpumask());
/*
* The regular update, every sysctl_stat_interval, may come later
@@ -1896,7 +1915,9 @@ 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);
+ err = schedule_on_each_cpumask(refresh_vm_stats, dstmask);
+ free_cpumask_var(dstmask);
+
if (err)
return err;
for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
