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rcu: Export RCU_FAST_NO_HZ parameters to sysfs

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RCU_FAST_NO_HZ operation is controlled by four compile-time C-preprocessor
macros, but some use cases benefit greatly from runtime adjustment,
particularly when tuning devices.  This commit therefore creates the
corresponding sysfs entries.

Reported-by: Robin Randhawa <robin.randhawa@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2012-12-12 12:35:29 -08:00 committed by Paul E. McKenney
parent a488985851
commit 5e44ce35a6
1 changed files with 20 additions and 11 deletions
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31
kernel/rcutree_plugin.h
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@ -1617,6 +1617,15 @@ static void rcu_idle_count_callbacks_posted(void)
#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */
#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */
static int rcu_idle_flushes = RCU_IDLE_FLUSHES;
module_param(rcu_idle_flushes, int, 0644);
static int rcu_idle_opt_flushes = RCU_IDLE_OPT_FLUSHES;
module_param(rcu_idle_opt_flushes, int, 0644);
static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY;
module_param(rcu_idle_gp_delay, int, 0644);
static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY;
module_param(rcu_idle_lazy_gp_delay, int, 0644);
extern int tick_nohz_enabled;
/*
@ -1696,10 +1705,10 @@ int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
}
/* Set up for the possibility that RCU will post a timer. */
if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
*delta_jiffies = round_up(RCU_IDLE_GP_DELAY + jiffies,
RCU_IDLE_GP_DELAY) - jiffies;
*delta_jiffies = round_up(rcu_idle_gp_delay + jiffies,
rcu_idle_gp_delay) - jiffies;
} else {
*delta_jiffies = jiffies + RCU_IDLE_LAZY_GP_DELAY;
*delta_jiffies = jiffies + rcu_idle_lazy_gp_delay;
*delta_jiffies = round_jiffies(*delta_jiffies) - jiffies;
}
return 0;
@ -1805,11 +1814,11 @@ static void rcu_prepare_for_idle(int cpu)
if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
trace_rcu_prep_idle("User dyntick with callbacks");
rdtp->idle_gp_timer_expires =
round_up(jiffies + RCU_IDLE_GP_DELAY,
RCU_IDLE_GP_DELAY);
round_up(jiffies + rcu_idle_gp_delay,
rcu_idle_gp_delay);
} else if (rcu_cpu_has_callbacks(cpu)) {
rdtp->idle_gp_timer_expires =
round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY);
round_jiffies(jiffies + rcu_idle_lazy_gp_delay);
trace_rcu_prep_idle("User dyntick with lazy callbacks");
} else {
return;
@ -1861,8 +1870,8 @@ static void rcu_prepare_for_idle(int cpu)
/* Check and update the ->dyntick_drain sequencing. */
if (rdtp->dyntick_drain <= 0) {
/* First time through, initialize the counter. */
rdtp->dyntick_drain = RCU_IDLE_FLUSHES;
} else if (rdtp->dyntick_drain <= RCU_IDLE_OPT_FLUSHES &&
rdtp->dyntick_drain = rcu_idle_flushes;
} else if (rdtp->dyntick_drain <= rcu_idle_opt_flushes &&
!rcu_pending(cpu) &&
!local_softirq_pending()) {
/* Can we go dyntick-idle despite still having callbacks? */
@ -1871,11 +1880,11 @@ static void rcu_prepare_for_idle(int cpu)
if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
trace_rcu_prep_idle("Dyntick with callbacks");
rdtp->idle_gp_timer_expires =
round_up(jiffies + RCU_IDLE_GP_DELAY,
RCU_IDLE_GP_DELAY);
round_up(jiffies + rcu_idle_gp_delay,
rcu_idle_gp_delay);
} else {
rdtp->idle_gp_timer_expires =
round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY);
round_jiffies(jiffies + rcu_idle_lazy_gp_delay);
trace_rcu_prep_idle("Dyntick with lazy callbacks");
}
tp = &rdtp->idle_gp_timer;