rcu: Don't track sysidle state if no nohz_full= CPUs
If there are no nohz_full= CPUs, then there is currently no reason to
track sysidle state. This commit therefore short-circuits this state
tracking if !tick_nohz_full_enabled().
Note that these checks will need to be revisited if nohz_full= state
can ever be changed at runtime.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index e31fa71..c31eb28 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2679,6 +2679,10 @@
{
unsigned long j;
+ /* If there are no nohz_full= CPUs, no need to track this. */
+ if (!tick_nohz_full_enabled())
+ return;
+
/* Adjust nesting, check for fully idle. */
if (irq) {
rdtp->dynticks_idle_nesting--;
@@ -2744,6 +2748,10 @@
*/
static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq)
{
+ /* If there are no nohz_full= CPUs, no need to track this. */
+ if (!tick_nohz_full_enabled())
+ return;
+
/* Adjust nesting, check for already non-idle. */
if (irq) {
rdtp->dynticks_idle_nesting++;
@@ -2798,6 +2806,10 @@
unsigned long j;
struct rcu_dynticks *rdtp = rdp->dynticks;
+ /* If there are no nohz_full= CPUs, don't check system-wide idleness. */
+ if (!tick_nohz_full_enabled())
+ return;
+
/*
* If some other CPU has already reported non-idle, if this is
* not the flavor of RCU that tracks sysidle state, or if this
@@ -2924,6 +2936,10 @@
static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
unsigned long maxj)
{
+ /* If there are no nohz_full= CPUs, no need to track this. */
+ if (!tick_nohz_full_enabled())
+ return;
+
rcu_sysidle_report(rsp, isidle, maxj, true);
}
@@ -2950,7 +2966,8 @@
/*
* Check to see if the system is fully idle, other than the timekeeping CPU.
- * The caller must have disabled interrupts.
+ * The caller must have disabled interrupts. This is not intended to be
+ * called unless tick_nohz_full_enabled().
*/
bool rcu_sys_is_idle(void)
{
