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rcu: Don't track sysidle state if no nohz_full= CPUs

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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>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
This commit is contained in:
Paul E. McKenney 2014-07-21 11:34:33 -07:00
parent 417e8d2655
commit 663e131090
1 changed files with 18 additions and 1 deletions
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19
kernel/rcu/tree_plugin.h
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@ -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)
{