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sched: rt time limit 

Very simple time limit on the realtime scheduling classes.
Allow the rq's realtime class to consume sched_rt_ratio of every
sched_rt_period slice. If the class exceeds this quota the fair class
will preempt the realtime class.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-01-25 21:08:29 +01:00 committed by Ingo Molnar
parent 8f4d37ec07
commit fa85ae2418
4 changed files with 122 additions and 21 deletions
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2
include/linux/sched.h
View File

@ -1490,6 +1490,8 @@ extern unsigned int sysctl_sched_child_runs_first;
extern unsigned int sysctl_sched_features;
extern unsigned int sysctl_sched_migration_cost;
extern unsigned int sysctl_sched_nr_migrate;
extern unsigned int sysctl_sched_rt_period;
extern unsigned int sysctl_sched_rt_ratio;
#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
extern unsigned int sysctl_sched_min_bal_int_shares;
extern unsigned int sysctl_sched_max_bal_int_shares;

70
kernel/sched.c
View File

@ -342,13 +342,14 @@ struct cfs_rq {
/* Real-Time classes' related field in a runqueue: */
struct rt_rq {
struct rt_prio_array active;
int rt_load_balance_idx;
struct list_head *rt_load_balance_head, *rt_load_balance_curr;
unsigned long rt_nr_running;
#ifdef CONFIG_SMP
unsigned long rt_nr_migratory;
/* highest queued rt task prio */
int highest_prio;
int highest_prio; /* highest queued rt task prio */
int overloaded;
#endif
u64 rt_time;
u64 rt_throttled;
};
#ifdef CONFIG_SMP
@ -415,6 +416,7 @@ struct rq {
struct list_head leaf_cfs_rq_list;
#endif
struct rt_rq rt;
u64 rt_period_expire;
/*
* This is part of a global counter where only the total sum
@ -600,6 +602,21 @@ const_debug unsigned int sysctl_sched_features =
*/
const_debug unsigned int sysctl_sched_nr_migrate = 32;
/*
* period over which we measure -rt task cpu usage in ms.
* default: 1s
*/
const_debug unsigned int sysctl_sched_rt_period = 1000;
#define SCHED_RT_FRAC_SHIFT 16
#define SCHED_RT_FRAC (1UL << SCHED_RT_FRAC_SHIFT)
/*
* ratio of time -rt tasks may consume.
* default: 100%
*/
const_debug unsigned int sysctl_sched_rt_ratio = SCHED_RT_FRAC;
/*
* For kernel-internal use: high-speed (but slightly incorrect) per-cpu
* clock constructed from sched_clock():
@ -3674,8 +3691,8 @@ void scheduler_tick(void)
rq->clock = next_tick;
rq->tick_timestamp = rq->clock;
update_cpu_load(rq);
if (curr != rq->idle) /* FIXME: needed? */
curr->sched_class->task_tick(rq, curr, 0);
curr->sched_class->task_tick(rq, curr, 0);
update_sched_rt_period(rq);
spin_unlock(&rq->lock);
#ifdef CONFIG_SMP
@ -7041,6 +7058,29 @@ static void init_cfs_rq(struct cfs_rq *cfs_rq, struct rq *rq)
cfs_rq->min_vruntime = (u64)(-(1LL << 20));
}
static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
{
struct rt_prio_array *array;
int i;
array = &rt_rq->active;
for (i = 0; i < MAX_RT_PRIO; i++) {
INIT_LIST_HEAD(array->queue + i);
__clear_bit(i, array->bitmap);
}
/* delimiter for bitsearch: */
__set_bit(MAX_RT_PRIO, array->bitmap);
#ifdef CONFIG_SMP
rt_rq->rt_nr_migratory = 0;
rt_rq->highest_prio = MAX_RT_PRIO;
rt_rq->overloaded = 0;
#endif
rt_rq->rt_time = 0;
rt_rq->rt_throttled = 0;
}
void __init sched_init(void)
{
int highest_cpu = 0;
@ -7051,7 +7091,6 @@ void __init sched_init(void)
#endif
for_each_possible_cpu(i) {
struct rt_prio_array *array;
struct rq *rq;
rq = cpu_rq(i);
@ -7083,6 +7122,8 @@ void __init sched_init(void)
}
init_task_group.shares = init_task_group_load;
#endif
init_rt_rq(&rq->rt, rq);
rq->rt_period_expire = 0;
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
rq->cpu_load[j] = 0;
@ -7095,22 +7136,11 @@ void __init sched_init(void)
rq->cpu = i;
rq->migration_thread = NULL;
INIT_LIST_HEAD(&rq->migration_queue);
rq->rt.highest_prio = MAX_RT_PRIO;
rq->rt.overloaded = 0;
rq_attach_root(rq, &def_root_domain);
#endif
init_rq_hrtick(rq);
atomic_set(&rq->nr_iowait, 0);
array = &rq->rt.active;
for (j = 0; j < MAX_RT_PRIO; j++) {
INIT_LIST_HEAD(array->queue + j);
__clear_bit(j, array->bitmap);
}
highest_cpu = i;
/* delimiter for bitsearch: */
__set_bit(MAX_RT_PRIO, array->bitmap);
}
set_load_weight(&init_task);
@ -7282,7 +7312,7 @@ void set_curr_task(int cpu, struct task_struct *p)
#ifdef CONFIG_SMP
/*
* distribute shares of all task groups among their schedulable entities,
* to reflect load distrbution across cpus.
* to reflect load distribution across cpus.
*/
static int rebalance_shares(struct sched_domain *sd, int this_cpu)
{
@ -7349,7 +7379,7 @@ static int rebalance_shares(struct sched_domain *sd, int this_cpu)
* sysctl_sched_max_bal_int_shares represents the maximum interval between
* consecutive calls to rebalance_shares() in the same sched domain.
*
* These settings allows for the appropriate tradeoff between accuracy of
* These settings allows for the appropriate trade-off between accuracy of
* fairness and the associated overhead.
*
*/

53
kernel/sched_rt.c
View File

@ -45,6 +45,50 @@ static void update_rt_migration(struct rq *rq)
}
#endif /* CONFIG_SMP */
static int sched_rt_ratio_exceeded(struct rq *rq, struct rt_rq *rt_rq)
{
u64 period, ratio;
if (sysctl_sched_rt_ratio == SCHED_RT_FRAC)
return 0;
if (rt_rq->rt_throttled)
return 1;
period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
ratio = (period * sysctl_sched_rt_ratio) >> SCHED_RT_FRAC_SHIFT;
if (rt_rq->rt_time > ratio) {
rt_rq->rt_throttled = rq->clock + period - rt_rq->rt_time;
return 1;
}
return 0;
}
static void update_sched_rt_period(struct rq *rq)
{
while (rq->clock > rq->rt_period_expire) {
u64 period, ratio;
period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
ratio = (period * sysctl_sched_rt_ratio) >> SCHED_RT_FRAC_SHIFT;
rq->rt.rt_time -= min(rq->rt.rt_time, ratio);
rq->rt_period_expire += period;
}
/*
* When the rt throttle is expired, let them rip.
* (XXX: use hrtick when available)
*/
if (rq->rt.rt_throttled && rq->clock > rq->rt.rt_throttled) {
rq->rt.rt_throttled = 0;
if (!sched_rt_ratio_exceeded(rq, &rq->rt))
resched_task(rq->curr);
}
}
/*
* Update the current task's runtime statistics. Skip current tasks that
* are not in our scheduling class.
@ -66,6 +110,11 @@ static void update_curr_rt(struct rq *rq)
curr->se.sum_exec_runtime += delta_exec;
curr->se.exec_start = rq->clock;
cpuacct_charge(curr, delta_exec);
rq->rt.rt_time += delta_exec;
update_sched_rt_period(rq);
if (sched_rt_ratio_exceeded(rq, &rq->rt))
resched_task(curr);
}
static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq)
@ -208,8 +257,12 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
struct rt_prio_array *array = &rq->rt.active;
struct task_struct *next;
struct list_head *queue;
struct rt_rq *rt_rq = &rq->rt;
int idx;
if (sched_rt_ratio_exceeded(rq, rt_rq))
return NULL;
idx = sched_find_first_bit(array->bitmap);
if (idx >= MAX_RT_PRIO)
return NULL;

18
kernel/sysctl.c
View File

@ -306,7 +306,23 @@ static struct ctl_table kern_table[] = {
.procname = "sched_nr_migrate",
.data = &sysctl_sched_nr_migrate,
.maxlen = sizeof(unsigned int),
.mode = 644,
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "sched_rt_period_ms",
.data = &sysctl_sched_rt_period,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "sched_rt_ratio",
.data = &sysctl_sched_rt_ratio,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)