@@ -1406,10 +1406,15 @@ static void vmstat_update(struct work_struct *w)
* Counters were updated so we expect more updates
* to occur in the future. Keep on running the
* update worker thread.
+ * If we were marked on cpu_stat_off clear the flag
+ * so that vmstat_shepherd doesn't schedule us again.
*/
- queue_delayed_work_on(smp_processor_id(), vmstat_wq,
- this_cpu_ptr(&vmstat_work),
- round_jiffies_relative(sysctl_stat_interval));
+ if (!cpumask_test_and_clear_cpu(smp_processor_id(),
+ cpu_stat_off)) {
+ queue_delayed_work_on(smp_processor_id(), vmstat_wq,
+ this_cpu_ptr(&vmstat_work),
+ round_jiffies_relative(sysctl_stat_interval));
+ }
} else {
/*
* We did not update any counters so the app may be in
@@ -1437,18 +1442,6 @@ static void vmstat_update(struct work_struct *w)
* until the diffs stay at zero. The function is used by NOHZ and can only be
* invoked when tick processing is not active.
*/
-void quiet_vmstat(void)
-{
- if (system_state != SYSTEM_RUNNING)
- return;
-
- do {
- if (!cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))
- cancel_delayed_work(this_cpu_ptr(&vmstat_work));
-
- } while (refresh_cpu_vm_stats(false));
-}
-
/*
* Check if the diffs for a certain cpu indicate that
* an update is needed.
@@ -1472,6 +1465,30 @@ static bool need_update(int cpu)
return false;
}
+void quiet_vmstat(void)
+{
+ if (system_state != SYSTEM_RUNNING)
+ return;
+
+ /*
+ * If we are already in hands of the shepherd then there
+ * is nothing for us to do here.
+ */
+ if (cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))
+ return;
+
+ if (!need_update(smp_processor_id()))
+ return;
+
+ /*
+ * Just refresh counters and do not care about the pending delayed
+ * vmstat_update. It doesn't fire that often to matter and canceling
+ * it would be too expensive from this path.
+ * vmstat_shepherd will take care about that for us.
+ */
+ refresh_cpu_vm_stats(false);
+}
+
/*
* Shepherd worker thread that checks the
@@ -1489,18 +1506,25 @@ static void vmstat_shepherd(struct work_struct *w)
get_online_cpus();
/* Check processors whose vmstat worker threads have been disabled */
- for_each_cpu(cpu, cpu_stat_off)
- if (need_update(cpu) &&
- cpumask_test_and_clear_cpu(cpu, cpu_stat_off))
-
- queue_delayed_work_on(cpu, vmstat_wq,
- &per_cpu(vmstat_work, cpu), 0);
+ for_each_cpu(cpu, cpu_stat_off) {
+ struct delayed_work *dw = &per_cpu(vmstat_work, cpu);
+ if (need_update(cpu)) {
+ if (cpumask_test_and_clear_cpu(cpu, cpu_stat_off))
+ queue_delayed_work_on(cpu, vmstat_wq, dw, 0);
+ } else {
+ /*
+ * Cancel the work if quiet_vmstat has put this
+ * cpu on cpu_stat_off because the work item might
+ * be still scheduled
+ */
+ cancel_delayed_work(dw);
+ }
+ }
put_online_cpus();
schedule_delayed_work(&shepherd,
round_jiffies_relative(sysctl_stat_interval));
-
}
static void __init start_shepherd_timer(void)