rcu: Expedited grace-period sleeps to idle priority

paulmckrcu · paulmckrcu · commit 68c2f27e01f6 · 2020-06-29T11:58:50.000-07:00
This commit converts the schedule_timeout_uninterruptible() call used
by RCU's expedited grace-period processing to schedule_timeout_idle().
This conversion avoids polluting the load-average with RCU-related
sleeping.

Signed-off-by: Paul E. McKenney &lt;paulmck@kernel.org&gt;
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
@@ -403,7 +403,7 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 			/* Online, so delay for a bit and try again. */
 			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 			trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("selectofl"));
-			schedule_timeout_uninterruptible(1);
+			schedule_timeout_idle(1);
 			goto retry_ipi;
 		}
 		/* CPU really is offline, so we must report its QS. */

Original file line number	Diff line number	Diff line change
`@@ -403,7 +403,7 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)`
`403`	`403`	`/* Online, so delay for a bit and try again. */`
`404`	`404`	`raw_spin_unlock_irqrestore_rcu_node(rnp, flags);`
`405`	`405`	`trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("selectofl"));`
`406`		`- schedule_timeout_uninterruptible(1);`
	`406`	`+ schedule_timeout_idle(1);`
`407`	`407`	`goto retry_ipi;`
`408`	`408`	`}`
`409`	`409`	`/* CPU really is offline, so we must report its QS. */`