Commit-ID: 663e131090dd10bac9dc0b4f5b624dd3211b20f6
Gitweb: http://git.kernel.org/tip/663e131090dd10bac9dc0b4f5b624dd3211b20f6
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 21 Jul 2014 11:34:33 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 16 Sep 2014 10:08:02 -0700
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@xxxxxxxxxxxxxxxxxx>
Acked-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Tested-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
kernel/rcu/tree_plugin.h | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 3ddad4f..d5aec54 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2707,6 +2707,10 @@ static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq)
{
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--;
@@ -2772,6 +2776,10 @@ void rcu_sysidle_force_exit(void)
*/
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++;
@@ -2826,6 +2834,10 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
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
@@ -2952,6 +2964,10 @@ static void rcu_sysidle_report(struct rcu_state *rsp, int isidle,
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);
}
@@ -2978,7 +2994,8 @@ static void rcu_sysidle_cb(struct rcu_head *rhp)
/*
* 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)
{
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|