@@ -3,7 +3,10 @@
* EDF scheduling is a real-time scheduling algorithm used in embedded field.
*
* by Sisu Xi, 2013, Washington University in Saint Louis
- * and Meng Xu, 2014, University of Pennsylvania
+ * Meng Xu, 2014-2016, University of Pennsylvania
+ *
+ * Conversion toward event driven model by Tianyang Chen
+ * and Dagaen Golomb, 2016, University of Pennsylvania
*
* based on the code of credit Scheduler
*/
@@ -16,6 +19,7 @@
#include <xen/delay.h>
#include <xen/event.h>
#include <xen/time.h>
+#include <xen/timer.h>
#include <xen/perfc.h>
#include <xen/sched-if.h>
#include <xen/softirq.h>
@@ -87,7 +91,7 @@
#define RTDS_DEFAULT_BUDGET (MICROSECS(4000))
#define UPDATE_LIMIT_SHIFT 10
-#define MAX_SCHEDULE (MILLISECS(1))
+
/*
* Flags
*/
@@ -115,6 +119,16 @@
#define RTDS_delayed_runq_add (1<<__RTDS_delayed_runq_add)
/*
+ * RTDS_depleted: Does this vcp run out of budget?
+ * This flag is
+ * + set in burn_budget() if a vcpu has zero budget left;
+ * + cleared and checked in the repenishment handler,
+ * for the vcpus that are being replenished.
+ */
+#define __RTDS_depleted 3
+#define RTDS_depleted (1<<__RTDS_depleted)
+
+/*
* rt tracing events ("only" 512 available!). Check
* include/public/trace.h for more details.
*/
@@ -142,6 +156,8 @@ static cpumask_var_t *_cpumask_scratch;
*/
static unsigned int nr_rt_ops;
+static void repl_timer_handler(void *data);
+
/*
* Systme-wide private data, include global RunQueue/DepletedQ
* Global lock is referenced by schedule_data.schedule_lock from all
@@ -152,7 +168,9 @@ struct rt_private {
struct list_head sdom; /* list of availalbe domains, used for dump */
struct list_head runq; /* ordered list of runnable vcpus */
struct list_head depletedq; /* unordered list of depleted vcpus */
+ struct list_head replq; /* ordered list of vcpus that need replenishment */
cpumask_t tickled; /* cpus been tickled */
+ struct timer *repl_timer; /* replenishment timer */
};
/*
@@ -160,6 +178,7 @@ struct rt_private {
*/
struct rt_vcpu {
struct list_head q_elem; /* on the runq/depletedq list */
+ struct list_head replq_elem; /* on the replenishment events list */
/* Up-pointers */
struct rt_dom *sdom;
@@ -213,8 +232,14 @@ static inline struct list_head *rt_depletedq(const struct scheduler *ops)
return &rt_priv(ops)->depletedq;
}
+static inline struct list_head *rt_replq(const struct scheduler *ops)
+{
+ return &rt_priv(ops)->replq;
+}
+
/*
- * Queue helper functions for runq and depletedq
+ * Helper functions for manipulating the runqueue, the depleted queue,
+ * and the replenishment events queue.
*/
static int
__vcpu_on_q(const struct rt_vcpu *svc)
@@ -228,6 +253,18 @@ __q_elem(struct list_head *elem)
return list_entry(elem, struct rt_vcpu, q_elem);
}
+static struct rt_vcpu *
+replq_elem(struct list_head *elem)
+{
+ return list_entry(elem, struct rt_vcpu, replq_elem);
+}
+
+static int
+vcpu_on_replq(const struct rt_vcpu *svc)
+{
+ return !list_empty(&svc->replq_elem);
+}
+
/*
* Debug related code, dump vcpu/cpu information
*/
@@ -288,7 +325,7 @@ rt_dump_pcpu(const struct scheduler *ops, int cpu)
static void
rt_dump(const struct scheduler *ops)
{
- struct list_head *runq, *depletedq, *iter;
+ struct list_head *runq, *depletedq, *replq, *iter;
struct rt_private *prv = rt_priv(ops);
struct rt_vcpu *svc;
struct rt_dom *sdom;
@@ -301,6 +338,7 @@ rt_dump(const struct scheduler *ops)
runq = rt_runq(ops);
depletedq = rt_depletedq(ops);
+ replq = rt_replq(ops);
printk("Global RunQueue info:\n");
list_for_each( iter, runq )
@@ -316,6 +354,13 @@ rt_dump(const struct scheduler *ops)
rt_dump_vcpu(ops, svc);
}
+ printk("Global Replenishment Events info:\n");
+ list_for_each( iter, replq )
+ {
+ svc = replq_elem(iter);
+ rt_dump_vcpu(ops, svc);
+ }
+
printk("Domain info:\n");
list_for_each( iter, &prv->sdom )
{
@@ -380,11 +425,84 @@ rt_update_deadline(s_time_t now, struct rt_vcpu *svc)
return;
}
+/*
+ * Helpers for removing and inserting a vcpu in a queue
+ * that is being kept ordered by the vcpus' deadlines (as EDF
+ * mandates).
+ *
+ * For callers' convenience, the vcpu removing helper returns
+ * true if the vcpu removed was the one at the front of the
+ * queue; similarly, the inserting helper returns true if the
+ * inserted ended at the front of the queue (i.e., in both
+ * cases, if the vcpu with the earliest deadline is what we
+ * are dealing with).
+ */
+static inline bool_t
+deadline_queue_remove(struct list_head *queue, struct list_head *elem)
+{
+ int pos = 0;
+
+ if ( queue->next != elem )
+ pos = 1;
+
+ list_del_init(elem);
+ return !pos;
+}
+
+static inline bool_t
+deadline_queue_insert(struct rt_vcpu * (*qelem)(struct list_head *),
+ struct rt_vcpu *svc, struct list_head *elem,
+ struct list_head *queue)
+{
+ struct list_head *iter;
+ int pos = 0;
+
+ list_for_each ( iter, queue )
+ {
+ struct rt_vcpu * iter_svc = (*qelem)(iter);
+ if ( svc->cur_deadline <= iter_svc->cur_deadline )
+ break;
+ pos++;
+ }
+ list_add_tail(elem, iter);
+ return !pos;
+}
+#define deadline_runq_insert(...) \
+ deadline_queue_insert(&__q_elem, ##__VA_ARGS__)
+#define deadline_replq_insert(...) \
+ deadline_queue_insert(&replq_elem, ##__VA_ARGS__)
+
static inline void
__q_remove(struct rt_vcpu *svc)
{
- if ( __vcpu_on_q(svc) )
- list_del_init(&svc->q_elem);
+ ASSERT( __vcpu_on_q(svc) );
+ list_del_init(&svc->q_elem);
+}
+
+static inline void
+replq_remove(const struct scheduler *ops, struct rt_vcpu *svc)
+{
+ struct rt_private *prv = rt_priv(ops);
+ struct list_head *replq = rt_replq(ops);
+
+ ASSERT( vcpu_on_replq(svc) );
+
+ if ( deadline_queue_remove(replq, &svc->replq_elem) )
+ {
+ /*
+ * The replenishment timer needs to be set to fire when a
+ * replenishment for the vcpu at the front of the replenishment
+ * queue is due. If it is such vcpu that we just removed, we may
+ * need to reprogram the timer.
+ */
+ if ( !list_empty(replq) )
+ {
+ struct rt_vcpu *svc_next = replq_elem(replq->next);
+ set_timer(prv->repl_timer, svc_next->cur_deadline);
+ }
+ else
+ stop_timer(prv->repl_timer);
+ }
}
/*
@@ -397,27 +515,69 @@ __runq_insert(const struct scheduler *ops, struct rt_vcpu *svc)
{
struct rt_private *prv = rt_priv(ops);
struct list_head *runq = rt_runq(ops);
- struct list_head *iter;
ASSERT( spin_is_locked(&prv->lock) );
-
ASSERT( !__vcpu_on_q(svc) );
+ ASSERT( vcpu_on_replq(svc) );
/* add svc to runq if svc still has budget */
if ( svc->cur_budget > 0 )
- {
- list_for_each(iter, runq)
- {
- struct rt_vcpu * iter_svc = __q_elem(iter);
- if ( svc->cur_deadline <= iter_svc->cur_deadline )
- break;
- }
- list_add_tail(&svc->q_elem, iter);
- }
+ deadline_runq_insert(svc, &svc->q_elem, runq);
else
- {
list_add(&svc->q_elem, &prv->depletedq);
+}
+
+static void
+replq_insert(const struct scheduler *ops, struct rt_vcpu *svc)
+{
+ struct list_head *replq = rt_replq(ops);
+ struct rt_private *prv = rt_priv(ops);
+
+ ASSERT( !vcpu_on_replq(svc) );
+
+ /*
+ * The timer may be re-programmed if svc is inserted
+ * at the front of the event list.
+ */
+ if ( deadline_replq_insert(svc, &svc->replq_elem, replq) )
+ set_timer(prv->repl_timer, svc->cur_deadline);
+}
+
+/*
+ * Removes and re-inserts an event to the replenishment queue.
+ * The aim is to update its position inside the queue, as its
+ * deadline (and hence its replenishment time) could have
+ * changed.
+ */
+static void
+replq_reinsert(const struct scheduler *ops, struct rt_vcpu *svc)
+{
+ struct list_head *replq = rt_replq(ops);
+ struct rt_vcpu *rearm_svc = svc;
+ bool_t rearm = 0;
+
+ ASSERT( vcpu_on_replq(svc) );
+
+ /*
+ * If svc was at the front of the replenishment queue, we certainly
+ * need to re-program the timer, and we want to use the deadline of
+ * the vcpu which is now at the front of the queue (which may still
+ * be svc or not).
+ *
+ * We may also need to re-program, if svc has been put at the front
+ * of the replenishment queue when being re-inserted.
+ */
+ if ( deadline_queue_remove(replq, &svc->replq_elem) )
+ {
+ deadline_replq_insert(svc, &svc->replq_elem, replq);
+ rearm_svc = replq_elem(replq->next);
+ rearm = 1;
}
+ else
+ rearm = deadline_replq_insert(svc, &svc->replq_elem, replq);
+
+ if ( rearm )
+ set_timer(rt_priv(ops)->repl_timer, rearm_svc->cur_deadline);
}
/*
@@ -449,11 +609,18 @@ rt_init(struct scheduler *ops)
INIT_LIST_HEAD(&prv->sdom);
INIT_LIST_HEAD(&prv->runq);
INIT_LIST_HEAD(&prv->depletedq);
+ INIT_LIST_HEAD(&prv->replq);
cpumask_clear(&prv->tickled);
ops->sched_data = prv;
+ /*
+ * The timer initialization will happen later when
+ * the first pcpu is added to this pool in alloc_pdata.
+ */
+ prv->repl_timer = NULL;
+
return 0;
no_mem:
@@ -473,6 +640,10 @@ rt_deinit(struct scheduler *ops)
xfree(_cpumask_scratch);
_cpumask_scratch = NULL;
}
+
+ kill_timer(prv->repl_timer);
+ xfree(prv->repl_timer);
+
ops->sched_data = NULL;
xfree(prv);
}
@@ -494,6 +665,17 @@ rt_alloc_pdata(const struct scheduler *ops, int cpu)
if ( !alloc_cpumask_var(&_cpumask_scratch[cpu]) )
return NULL;
+ if ( prv->repl_timer == NULL )
+ {
+ /* Allocate the timer on the first cpu of this pool. */
+ prv->repl_timer = xzalloc(struct timer);
+
+ if ( prv->repl_timer == NULL )
+ return NULL;
+
+ init_timer(prv->repl_timer, repl_timer_handler, (void *)ops, cpu);
+ }
+
/* 1 indicates alloc. succeed in schedule.c */
return (void *)1;
}
@@ -587,6 +769,7 @@ rt_alloc_vdata(const struct scheduler *ops, struct vcpu *vc, void *dd)
return NULL;
INIT_LIST_HEAD(&svc->q_elem);
+ INIT_LIST_HEAD(&svc->replq_elem);
svc->flags = 0U;
svc->sdom = dd;
svc->vcpu = vc;
@@ -610,7 +793,8 @@ rt_free_vdata(const struct scheduler *ops, void *priv)
}
/*
- * This function is called in sched_move_domain() in schedule.c
+ * It is called in sched_move_domain() and sched_init_vcpu
+ * in schedule.c.
* When move a domain to a new cpupool.
* It inserts vcpus of moving domain to the scheduler's RunQ in
* dest. cpupool.
@@ -628,8 +812,13 @@ rt_vcpu_insert(const struct scheduler *ops, struct vcpu *vc)
if ( now >= svc->cur_deadline )
rt_update_deadline(now, svc);
- if ( !__vcpu_on_q(svc) && vcpu_runnable(vc) && !vc->is_running )
- __runq_insert(ops, svc);
+ if ( !__vcpu_on_q(svc) && vcpu_runnable(vc) )
+ {
+ replq_insert(ops, svc);
+
+ if ( !vc->is_running )
+ __runq_insert(ops, svc);
+ }
vcpu_schedule_unlock_irq(lock, vc);
SCHED_STAT_CRANK(vcpu_insert);
@@ -652,6 +841,10 @@ rt_vcpu_remove(const struct scheduler *ops, struct vcpu *vc)
lock = vcpu_schedule_lock_irq(vc);
if ( __vcpu_on_q(svc) )
__q_remove(svc);
+
+ if ( vcpu_on_replq(svc) )
+ replq_remove(ops,svc);
+
vcpu_schedule_unlock_irq(lock, vc);
}
@@ -706,8 +899,11 @@ burn_budget(const struct scheduler *ops, struct rt_vcpu *svc, s_time_t now)
svc->cur_budget -= delta;
- if ( svc->cur_budget < 0 )
+ if ( svc->cur_budget <= 0 )
+ {
svc->cur_budget = 0;
+ set_bit(__RTDS_depleted, &svc->flags);
+ }
/* TRACE */
{
@@ -784,44 +980,6 @@ __runq_pick(const struct scheduler *ops, const cpumask_t *mask)
}
/*
- * Update vcpu's budget and
- * sort runq by insert the modifed vcpu back to runq
- * lock is grabbed before calling this function
- */
-static void
-__repl_update(const struct scheduler *ops, s_time_t now)
-{
- struct list_head *runq = rt_runq(ops);
- struct list_head *depletedq = rt_depletedq(ops);
- struct list_head *iter;
- struct list_head *tmp;
- struct rt_vcpu *svc = NULL;
-
- list_for_each_safe(iter, tmp, runq)
- {
- svc = __q_elem(iter);
- if ( now < svc->cur_deadline )
- break;
-
- rt_update_deadline(now, svc);
- /* reinsert the vcpu if its deadline is updated */
- __q_remove(svc);
- __runq_insert(ops, svc);
- }
-
- list_for_each_safe(iter, tmp, depletedq)
- {
- svc = __q_elem(iter);
- if ( now >= svc->cur_deadline )
- {
- rt_update_deadline(now, svc);
- __q_remove(svc); /* remove from depleted queue */
- __runq_insert(ops, svc); /* add to runq */
- }
- }
-}
-
-/*
* schedule function for rt scheduler.
* The lock is already grabbed in schedule.c, no need to lock here
*/
@@ -840,8 +998,6 @@ rt_schedule(const struct scheduler *ops, s_time_t now, bool_t tasklet_work_sched
/* burn_budget would return for IDLE VCPU */
burn_budget(ops, scurr, now);
- __repl_update(ops, now);
-
if ( tasklet_work_scheduled )
{
trace_var(TRC_RTDS_SCHED_TASKLET, 1, 0, NULL);
@@ -868,6 +1024,7 @@ rt_schedule(const struct scheduler *ops, s_time_t now, bool_t tasklet_work_sched
set_bit(__RTDS_delayed_runq_add, &scurr->flags);
snext->last_start = now;
+ ret.time = -1; /* if an idle vcpu is picked */
if ( !is_idle_vcpu(snext->vcpu) )
{
if ( snext != scurr )
@@ -880,9 +1037,8 @@ rt_schedule(const struct scheduler *ops, s_time_t now, bool_t tasklet_work_sched
snext->vcpu->processor = cpu;
ret.migrated = 1;
}
+ ret.time = snext->cur_budget; /* invoke the scheduler next time */
}
-
- ret.time = MIN(snext->budget, MAX_SCHEDULE); /* sched quantum */
ret.task = snext->vcpu;
return ret;
@@ -903,7 +1059,10 @@ rt_vcpu_sleep(const struct scheduler *ops, struct vcpu *vc)
if ( curr_on_cpu(vc->processor) == vc )
cpu_raise_softirq(vc->processor, SCHEDULE_SOFTIRQ);
else if ( __vcpu_on_q(svc) )
+ {
__q_remove(svc);
+ replq_remove(ops, svc);
+ }
else if ( svc->flags & RTDS_delayed_runq_add )
clear_bit(__RTDS_delayed_runq_add, &svc->flags);
}
@@ -1008,10 +1167,7 @@ rt_vcpu_wake(const struct scheduler *ops, struct vcpu *vc)
{
struct rt_vcpu * const svc = rt_vcpu(vc);
s_time_t now = NOW();
- struct rt_private *prv = rt_priv(ops);
- struct rt_vcpu *snext = NULL; /* highest priority on RunQ */
- struct rt_dom *sdom = NULL;
- cpumask_t *online;
+ bool_t missed;
BUG_ON( is_idle_vcpu(vc) );
@@ -1033,32 +1189,42 @@ rt_vcpu_wake(const struct scheduler *ops, struct vcpu *vc)
else
SCHED_STAT_CRANK(vcpu_wake_not_runnable);
- /* If context hasn't been saved for this vcpu yet, we can't put it on
- * the Runqueue/DepletedQ. Instead, we set a flag so that it will be
- * put on the Runqueue/DepletedQ after the context has been saved.
+ /*
+ * If a deadline passed while svc was asleep/blocked, we need new
+ * scheduling parameters (a new deadline and full budget).
+ */
+
+ missed = ( now >= svc->cur_deadline );
+ if ( missed )
+ rt_update_deadline(now, svc);
+
+ /*
+ * If context hasn't been saved for this vcpu yet, we can't put it on
+ * the run-queue/depleted-queue. Instead, we set the appropriate flag,
+ * the vcpu will be put back on queue after the context has been saved
+ * (in rt_context_save()).
*/
if ( unlikely(svc->flags & RTDS_scheduled) )
{
set_bit(__RTDS_delayed_runq_add, &svc->flags);
+ /*
+ * The vcpu is waking up already, and we didn't even had the time to
+ * remove its next replenishment event from the replenishment queue
+ * when it blocked! No big deal. If we did not miss the deadline in
+ * the meantime, let's just leave it there. If we did, let's remove it
+ * and queue a new one (to occur at our new deadline).
+ */
+ if ( missed )
+ replq_reinsert(ops, svc);
return;
}
- if ( now >= svc->cur_deadline)
- rt_update_deadline(now, svc);
-
+ /* Replenishment event got cancelled when we blocked. Add it back. */
+ replq_insert(ops, svc);
/* insert svc to runq/depletedq because svc is not in queue now */
__runq_insert(ops, svc);
- __repl_update(ops, now);
-
- ASSERT(!list_empty(&prv->sdom));
- sdom = list_entry(prv->sdom.next, struct rt_dom, sdom_elem);
- online = cpupool_domain_cpumask(sdom->dom);
- snext = __runq_pick(ops, online); /* pick snext from ALL valid cpus */
-
- runq_tickle(ops, snext);
-
- return;
+ runq_tickle(ops, svc);
}
/*
@@ -1069,10 +1235,6 @@ static void
rt_context_saved(const struct scheduler *ops, struct vcpu *vc)
{
struct rt_vcpu *svc = rt_vcpu(vc);
- struct rt_vcpu *snext = NULL;
- struct rt_dom *sdom = NULL;
- struct rt_private *prv = rt_priv(ops);
- cpumask_t *online;
spinlock_t *lock = vcpu_schedule_lock_irq(vc);
clear_bit(__RTDS_scheduled, &svc->flags);
@@ -1084,15 +1246,11 @@ rt_context_saved(const struct scheduler *ops, struct vcpu *vc)
likely(vcpu_runnable(vc)) )
{
__runq_insert(ops, svc);
- __repl_update(ops, NOW());
-
- ASSERT(!list_empty(&prv->sdom));
- sdom = list_entry(prv->sdom.next, struct rt_dom, sdom_elem);
- online = cpupool_domain_cpumask(sdom->dom);
- snext = __runq_pick(ops, online); /* pick snext from ALL cpus */
-
- runq_tickle(ops, snext);
+ runq_tickle(ops, svc);
}
+ else
+ replq_remove(ops, svc);
+
out:
vcpu_schedule_unlock_irq(lock, vc);
}
@@ -1150,6 +1308,85 @@ rt_dom_cntl(
return rc;
}
+/*
+ * The replenishment timer handler picks vcpus
+ * from the replq and does the actual replenishment.
+ */
+static void repl_timer_handler(void *data){
+ s_time_t now = NOW();
+ struct scheduler *ops = data;
+ struct rt_private *prv = rt_priv(ops);
+ struct list_head *replq = rt_replq(ops);
+ struct list_head *runq = rt_runq(ops);
+ struct timer *repl_timer = prv->repl_timer;
+ struct list_head *iter, *tmp;
+ struct rt_vcpu *svc;
+ LIST_HEAD(tmp_replq);
+
+ spin_lock_irq(&prv->lock);
+
+ /*
+ * Do the replenishment and move replenished vcpus
+ * to the temporary list to tickle.
+ * If svc is on run queue, we need to put it at
+ * the correct place since its deadline changes.
+ */
+ list_for_each_safe ( iter, tmp, replq )
+ {
+ svc = replq_elem(iter);
+
+ if ( now < svc->cur_deadline )
+ break;
+
+ list_del(&svc->replq_elem);
+ rt_update_deadline(now, svc);
+ list_add(&svc->replq_elem, &tmp_replq);
+
+ if ( __vcpu_on_q(svc) )
+ {
+ __q_remove(svc);
+ __runq_insert(ops, svc);
+ }
+ }
+
+ /*
+ * Iterate through the list of updated vcpus.
+ * If an updated vcpu is running, tickle the head of the
+ * runqueue if it has a higher priority.
+ * If an updated vcpu was depleted and on the runqueue, tickle it.
+ * Finally, reinsert the vcpus back to replenishement events list.
+ */
+ list_for_each_safe ( iter, tmp, &tmp_replq )
+ {
+ svc = replq_elem(iter);
+
+ if ( curr_on_cpu(svc->vcpu->processor) == svc->vcpu &&
+ !list_empty(runq) )
+ {
+ struct rt_vcpu *next_on_runq = __q_elem(runq->next);
+
+ if ( svc->cur_deadline > next_on_runq->cur_deadline )
+ runq_tickle(ops, next_on_runq);
+ }
+ else if ( __vcpu_on_q(svc) &&
+ test_and_clear_bit(__RTDS_depleted, &svc->flags) )
+ runq_tickle(ops, svc);
+
+ list_del(&svc->replq_elem);
+ deadline_replq_insert(svc, &svc->replq_elem, replq);
+ }
+
+ /*
+ * If there are vcpus left in the replenishment event list,
+ * set the next replenishment to happen at the deadline of
+ * the one in the front.
+ */
+ if ( !list_empty(replq) )
+ set_timer(repl_timer, replq_elem(replq->next)->cur_deadline);
+
+ spin_unlock_irq(&prv->lock);
+}
+
static const struct scheduler sched_rtds_def = {
.name = "SMP RTDS Scheduler",
.opt_name = "rtds",