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sched: Add a timer to handle CFS bandwidth refresh 

This patch adds a per-task_group timer which handles the refresh of the global
CFS bandwidth pool.

Since the RT pool is using a similar timer there's some small refactoring to
share this support.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.277271273@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul Turner 2011-07-21 09:43:31 -07:00 committed by Ingo Molnar
parent ec12cb7f31
commit 58088ad015
2 changed files with 123 additions and 24 deletions
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107
kernel/sched.c
View File

@ -196,10 +196,28 @@ static inline int rt_bandwidth_enabled(void)
return sysctl_sched_rt_runtime >= 0;
}
static void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period)
{
unsigned long delta;
ktime_t soft, hard, now;
for (;;) {
if (hrtimer_active(period_timer))
break;
now = hrtimer_cb_get_time(period_timer);
hrtimer_forward(period_timer, now, period);
soft = hrtimer_get_softexpires(period_timer);
hard = hrtimer_get_expires(period_timer);
delta = ktime_to_ns(ktime_sub(hard, soft));
__hrtimer_start_range_ns(period_timer, soft, delta,
HRTIMER_MODE_ABS_PINNED, 0);
}
}
static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
{
ktime_t now;
if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
return;
@ -207,22 +225,7 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
return;
raw_spin_lock(&rt_b->rt_runtime_lock);
for (;;) {
unsigned long delta;
ktime_t soft, hard;
if (hrtimer_active(&rt_b->rt_period_timer))
break;
now = hrtimer_cb_get_time(&rt_b->rt_period_timer);
hrtimer_forward(&rt_b->rt_period_timer, now, rt_b->rt_period);
soft = hrtimer_get_softexpires(&rt_b->rt_period_timer);
hard = hrtimer_get_expires(&rt_b->rt_period_timer);
delta = ktime_to_ns(ktime_sub(hard, soft));
__hrtimer_start_range_ns(&rt_b->rt_period_timer, soft, delta,
HRTIMER_MODE_ABS_PINNED, 0);
}
start_bandwidth_timer(&rt_b->rt_period_timer, rt_b->rt_period);
raw_spin_unlock(&rt_b->rt_runtime_lock);
}
@ -253,6 +256,9 @@ struct cfs_bandwidth {
ktime_t period;
u64 quota, runtime;
s64 hierarchal_quota;
int idle, timer_active;
struct hrtimer period_timer;
#endif
};
@ -403,6 +409,28 @@ static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
}
static inline u64 default_cfs_period(void);
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun);
static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
struct cfs_bandwidth *cfs_b =
container_of(timer, struct cfs_bandwidth, period_timer);
ktime_t now;
int overrun;
int idle = 0;
for (;;) {
now = hrtimer_cb_get_time(timer);
overrun = hrtimer_forward(timer, now, cfs_b->period);
if (!overrun)
break;
idle = do_sched_cfs_period_timer(cfs_b, overrun);
}
return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}
static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
@ -410,6 +438,9 @@ static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
cfs_b->runtime = 0;
cfs_b->quota = RUNTIME_INF;
cfs_b->period = ns_to_ktime(default_cfs_period());
hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
cfs_b->period_timer.function = sched_cfs_period_timer;
}
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
@ -417,8 +448,34 @@ static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
cfs_rq->runtime_enabled = 0;
}
/* requires cfs_b->lock, may release to reprogram timer */
static void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
/*
* The timer may be active because we're trying to set a new bandwidth
* period or because we're racing with the tear-down path
* (timer_active==0 becomes visible before the hrtimer call-back
* terminates). In either case we ensure that it's re-programmed
*/
while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
raw_spin_unlock(&cfs_b->lock);
/* ensure cfs_b->lock is available while we wait */
hrtimer_cancel(&cfs_b->period_timer);
raw_spin_lock(&cfs_b->lock);
/* if someone else restarted the timer then we're done */
if (cfs_b->timer_active)
return;
}
cfs_b->timer_active = 1;
start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
}
static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{}
{
hrtimer_cancel(&cfs_b->period_timer);
}
#else
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
@ -9078,7 +9135,7 @@ static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
{
int i, ret = 0;
int i, ret = 0, runtime_enabled;
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
if (tg == &root_task_group)
@ -9105,10 +9162,18 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
if (ret)
goto out_unlock;
runtime_enabled = quota != RUNTIME_INF;
raw_spin_lock_irq(&cfs_b->lock);
cfs_b->period = ns_to_ktime(period);
cfs_b->quota = quota;
cfs_b->runtime = quota;
/* restart the period timer (if active) to handle new period expiry */
if (runtime_enabled && cfs_b->timer_active) {
/* force a reprogram */
cfs_b->timer_active = 0;
__start_cfs_bandwidth(cfs_b);
}
raw_spin_unlock_irq(&cfs_b->lock);
for_each_possible_cpu(i) {
@ -9116,7 +9181,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
struct rq *rq = rq_of(cfs_rq);
raw_spin_lock_irq(&rq->lock);
cfs_rq->runtime_enabled = quota != RUNTIME_INF;
cfs_rq->runtime_enabled = runtime_enabled;
cfs_rq->runtime_remaining = 0;
raw_spin_unlock_irq(&rq->lock);
}

40
kernel/sched_fair.c
View File

@ -1284,9 +1284,16 @@ static void assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
raw_spin_lock(&cfs_b->lock);
if (cfs_b->quota == RUNTIME_INF)
amount = min_amount;
else if (cfs_b->runtime > 0) {
amount = min(cfs_b->runtime, min_amount);
cfs_b->runtime -= amount;
else {
/* ensure bandwidth timer remains active under consumption */
if (!cfs_b->timer_active)
__start_cfs_bandwidth(cfs_b);
if (cfs_b->runtime > 0) {
amount = min(cfs_b->runtime, min_amount);
cfs_b->runtime -= amount;
cfs_b->idle = 0;
}
}
raw_spin_unlock(&cfs_b->lock);
@ -1315,6 +1322,33 @@ static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
__account_cfs_rq_runtime(cfs_rq, delta_exec);
}
/*
* Responsible for refilling a task_group's bandwidth and unthrottling its
* cfs_rqs as appropriate. If there has been no activity within the last
* period the timer is deactivated until scheduling resumes; cfs_b->idle is
* used to track this state.
*/
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
{
int idle = 1;
raw_spin_lock(&cfs_b->lock);
/* no need to continue the timer with no bandwidth constraint */
if (cfs_b->quota == RUNTIME_INF)
goto out_unlock;
idle = cfs_b->idle;
cfs_b->runtime = cfs_b->quota;
/* mark as potentially idle for the upcoming period */
cfs_b->idle = 1;
out_unlock:
if (idle)
cfs_b->timer_active = 0;
raw_spin_unlock(&cfs_b->lock);
return idle;
}
#else
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
unsigned long delta_exec) {}