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| author |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-07-21 11:34:33 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-09-16 10:08:02 -0700 |
| commit | 663e131090dd10bac9dc0b4f5b624dd3211b20f6 (patch) | |
| tree | 88a47a1b26fe1af6a4c57a8e8bbee231b331c56d /kernel/rcu/tree_plugin.h | |
| parent | rcu: Eliminate redundant rcu_sysidle_state variable (diff) | |
| download | linux-dev-663e131090dd10bac9dc0b4f5b624dd3211b20f6.tar.xz linux-dev-663e131090dd10bac9dc0b4f5b624dd3211b20f6.zip | |
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>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'kernel/rcu/tree_plugin.h')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 3ddad4fb11a8..d5aec549558d 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) { |