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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v6][RFC]xen: sched: convert RTDS from time to event driven model
changes since v5:
removed unnecessary vcpu_on_replq() checks
deadline_queue_insert() returns a flag to indicate if it's
needed to re-program the timer
removed unnecessary timer checks
added helper functions to remove vcpus from queues
coding style
Changes since v4:
removed unnecessary replenishment queue checks in vcpu_wake()
extended replq_remove() to all cases in vcpu_sleep()
used _deadline_queue_insert() helper function for both queues
_replq_insert() and _replq_remove() program timer internally
Changes since v3:
removed running queue.
added repl queue to keep track of repl events.
timer is now per scheduler.
timer is init on a valid cpu in a cpupool.
Budget replenishment and enforcement are separated by adding
a replenishment timer, which fires at the next most imminent
release time of all runnable vcpus.
A new runningq has been added to keep track of all vcpus that
are on pcpus.
The following functions have major changes to manage the runningq
and replenishment
repl_handler(): It is a timer handler which is re-programmed
to fire at the nearest vcpu deadline to replenish vcpus on runq,
depeletedq and runningq. When the replenishment is done, each
replenished vcpu should tickle a pcpu to see if it needs to
preempt any running vcpus.
rt_schedule(): picks the highest runnable vcpu based on cpu
affinity and ret.time will be passed to schedule(). If an idle
vcpu is picked, -1 is returned to avoid busy-waiting. repl_update()
has been removed.
rt_vcpu_wake(): when a vcpu is awake, it tickles instead of
picking one from runq. When a vcpu wakes up, it might reprogram
the timer if it has a more recent release time.
rt_context_saved(): when context switching is finished, the
preempted vcpu will be put back into the runq. Runningq is
updated and picking from runq and tickling are removed.
Simplified funtional graph:
schedule.c SCHEDULE_SOFTIRQ:
rt_schedule():
[spin_lock]
burn_budget(scurr)
snext = runq_pick()
[spin_unlock]
sched_rt.c TIMER_SOFTIRQ
replenishment_timer_handler()
[spin_lock]
<for_each_vcpu_on_q(i)> {
replenish(i)
runq_tickle(i)
}>
program_timer()
[spin_lock]
Signed-off-by: Tianyang Chen <tiche@xxxxxxxxxxxxxx>
Signed-off-by: Meng Xu <mengxu@xxxxxxxxxxxxx>
Signed-off-by: Dagaen Golomb <dgolomb@xxxxxxxxxxxxxx>
---
xen/common/sched_rt.c | 328 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 244 insertions(+), 84 deletions(-)
diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 2e5430f..16f77f9 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -16,6 +16,7 @@
#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 +88,7 @@
#define RTDS_DEFAULT_BUDGET (MICROSECS(4000))
#define UPDATE_LIMIT_SHIFT 10
-#define MAX_SCHEDULE (MILLISECS(1))
+
/*
* Flags
*/
@@ -142,6 +143,9 @@ static cpumask_var_t *_cpumask_scratch;
*/
static unsigned int nr_rt_ops;
+/* handler for the replenishment timer */
+static void repl_handler(void *data);
+
/*
* Systme-wide private data, include global RunQueue/DepletedQ
* Global lock is referenced by schedule_data.schedule_lock from all
@@ -152,7 +156,9 @@ 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 +166,7 @@ struct rt_private {
*/
struct rt_vcpu {
struct list_head q_elem; /* on the runq/depletedq list */
+ struct list_head replq_elem;/* on the repl event list */
/* Up-pointers */
struct rt_dom *sdom;
@@ -213,8 +220,14 @@ 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
+ * Queue helper functions for runq, depletedq
+ * and replenishment event queue
*/
static int
__vcpu_on_q(const struct rt_vcpu *svc)
@@ -228,6 +241,18 @@ __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 +313,7 @@ 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 +326,7 @@ 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 +342,13 @@ rt_dump(const struct scheduler *ops)
rt_dump_vcpu(ops, svc);
}
+ printk("Global Replenishment Event 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 +413,74 @@ rt_update_deadline(s_time_t now, struct rt_vcpu *svc)
return;
}
+/* a helper function that only removes a vcpu from a queue */
+static inline void
+deadline_queue_remove(struct list_head *elem)
+{
+ list_del_init(elem);
+}
+
static inline void
__q_remove(struct rt_vcpu *svc)
{
if ( __vcpu_on_q(svc) )
- list_del_init(&svc->q_elem);
+ deadline_queue_remove(&svc->q_elem);
+}
+
+/*
+ * Removing a vcpu from the replenishment queue could
+ * re-program the timer for the next replenishment event
+ * if there is any on the list
+ */
+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);
+ struct timer* repl_timer = prv->repl_timer;
+
+ /*
+ * Disarm the timer before re-programming it.
+ * It doesn't matter if the vcpu to be removed
+ * is on top of the list or not because the timer
+ * is stopped and needs to be re-programmed anyways
+ */
+ stop_timer(repl_timer);
+
+ deadline_queue_remove(&svc->replq_elem);
+
+ /* re-arm the timer for the next replenishment event */
+ if( !list_empty(replq) )
+ {
+ struct rt_vcpu *svc_next = __replq_elem(replq->next);
+ set_timer(repl_timer, svc_next->cur_deadline);
+ }
+}
+
+/*
+ * An utility function that inserts a vcpu to a
+ * queue based on certain order (EDF). The returned
+ * value is 1 if a vcpu has been inserted to the
+ * front of a list
+ */
+static int
+deadline_queue_insert(struct rt_vcpu * (*_get_q_elem)(struct list_head *elem),
+ 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 = (*_get_q_elem)(iter);
+ if ( svc->cur_deadline <= iter_svc->cur_deadline )
+ break;
+
+ pos++;
+ }
+
+ list_add_tail(elem, iter);
+ return !pos;
}
/*
@@ -397,7 +493,6 @@ __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) );
@@ -405,22 +500,38 @@ __runq_insert(const struct scheduler *ops, struct rt_vcpu
*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_queue_insert(&__q_elem, svc, &svc->q_elem, runq);
else
{
list_add(&svc->q_elem, &prv->depletedq);
+ ASSERT( __vcpu_on_replq(svc) );
}
}
/*
+ * Insert svc into the replenishment event list
+ * in replenishment time order.
+ * vcpus that need to be replished earlier go first.
+ * The timer may be re-programmed if svc is inserted
+ * at the front of the event list.
+ */
+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);
+ struct timer *repl_timer = prv->repl_timer;
+ int set;
+
+ ASSERT( !__vcpu_on_replq(svc) );
+
+ set = deadline_queue_insert(&__replq_elem, svc, &svc->replq_elem, replq);
+
+ if( set )
+ set_timer(repl_timer,svc->cur_deadline);
+}
+
+/*
* Init/Free related code
*/
static int
@@ -449,11 +560,18 @@ 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 +591,10 @@ rt_deinit(const struct scheduler *ops)
xfree(_cpumask_scratch);
_cpumask_scratch = NULL;
}
+
+ kill_timer(prv->repl_timer);
+ xfree(prv->repl_timer);
+
xfree(prv);
}
@@ -493,6 +615,17 @@ 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_handler, (void *)ops, cpu);
+ }
+
/* 1 indicates alloc. succeed in schedule.c */
return (void *)1;
}
@@ -586,6 +719,7 @@ 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;
@@ -609,7 +743,8 @@ 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.
@@ -651,6 +786,10 @@ 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);
}
@@ -785,44 +924,6 @@ __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
*/
@@ -841,7 +942,6 @@ 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 )
{
@@ -868,6 +968,8 @@ 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 +982,11 @@ 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->budget; /* invoke the scheduler next time */
+
}
- ret.time = MIN(snext->budget, MAX_SCHEDULE); /* sched quantum */
ret.task = snext->vcpu;
/* TRACE */
@@ -924,6 +1028,8 @@ rt_vcpu_sleep(const struct scheduler *ops, struct vcpu *vc)
__q_remove(svc);
else if ( svc->flags & RTDS_delayed_runq_add )
clear_bit(__RTDS_delayed_runq_add, &svc->flags);
+
+ __replq_remove(ops, svc);
}
/*
@@ -1026,10 +1132,6 @@ 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;
BUG_ON( is_idle_vcpu(vc) );
@@ -1051,6 +1153,22 @@ rt_vcpu_wake(const struct scheduler *ops, struct vcpu
*vc)
else
SCHED_STAT_CRANK(vcpu_wake_not_runnable);
+ /*
+ * If a deadline passed while svc was asleep/blocked, we need new
+ * scheduling parameters ( a new deadline and full budget), and
+ * also a new replenishment event
+ */
+ if ( now >= svc->cur_deadline)
+ {
+ rt_update_deadline(now, svc);
+ __replq_remove(ops, svc);
+ }
+
+ if( !__vcpu_on_replq(svc) )
+ {
+ __replq_insert(ops, svc);
+ ASSERT( vcpu_runnable(vc) );
+ }
/* 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.
@@ -1061,22 +1179,10 @@ rt_vcpu_wake(const struct scheduler *ops, struct vcpu
*vc)
return;
}
- if ( now >= svc->cur_deadline)
- rt_update_deadline(now, 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);
}
/*
@@ -1087,10 +1193,6 @@ 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);
@@ -1102,14 +1204,7 @@ 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);
}
out:
vcpu_schedule_unlock_irq(lock, vc);
@@ -1168,6 +1263,71 @@ rt_dom_cntl(
return rc;
}
+/*
+ * The replenishment timer handler picks vcpus
+ * from the replq and does the actual replenishment
+ */
+static void repl_handler(void *data){
+ unsigned long flags;
+ s_time_t now = NOW();
+ struct scheduler *ops = data;
+ struct rt_private *prv = rt_priv(ops);
+ struct list_head *replq = rt_replq(ops);
+ struct timer *repl_timer = prv->repl_timer;
+ struct list_head *iter, *tmp;
+ struct rt_vcpu *svc = NULL;
+
+ spin_lock_irqsave(&prv->lock, flags);
+
+ stop_timer(repl_timer);
+
+ list_for_each_safe(iter, tmp, replq)
+ {
+ svc = __replq_elem(iter);
+
+ if ( now < svc->cur_deadline )
+ break;
+
+ rt_update_deadline(now, svc);
+
+ /*
+ * when the replenishment happens
+ * svc is either on a pcpu or on
+ * runq/depletedq
+ */
+ if( __vcpu_on_q(svc) )
+ {
+ /* put back to runq */
+ __q_remove(svc);
+ __runq_insert(ops, svc);
+ }
+
+ /*
+ * tickle regardless where it's at
+ * because a running vcpu could have
+ * a later deadline than others after
+ * replenishment
+ */
+ runq_tickle(ops, svc);
+
+ /*
+ * update replenishment event queue
+ * without reprogramming the timer
+ */
+ deadline_queue_remove(&svc->replq_elem);
+ deadline_queue_insert(&__replq_elem, svc, &svc->replq_elem, replq);
+ }
+
+ /*
+ * use the vcpu that's on the top
+ * or else don't program the timer
+ */
+ if( !list_empty(replq) )
+ set_timer(repl_timer, __replq_elem(replq->next)->cur_deadline);
+
+ spin_unlock_irqrestore(&prv->lock, flags);
+}
+
static struct rt_private _rt_priv;
static const struct scheduler sched_rtds_def = {
--
1.7.9.5
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