[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v8]xen: sched: convert RTDS from time to event driven model
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 replenishment queue has been added to keep track of all vcpus that are runnable. The following functions have major changes to manage the replenishment events and timer. repl_handler(): It is a timer handler which is re-programmed to fire at the nearest vcpu deadline to replenish 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 wakes up, it tickles instead of picking one from the run queue. rt_context_saved(): when context switching is finished, the preempted vcpu will be put back into the runq. 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> --- changes since v7: Coding sytle. Added a flag to indicate that a vcpu was depleted. Added a local list including updated vcpus in the timer handler. It is used to decide which vcpu should tickle. changes since v6: Removed unnecessary vcpu_on_q() checks for runq_insert() Renamed replenishment queue related functions without underscores New replq_reinsert() function for rt_vcpu_wake() 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. --- xen/common/sched_rt.c | 435 ++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 340 insertions(+), 95 deletions(-) diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c index bfed2e2..58189cd 100644 --- a/xen/common/sched_rt.c +++ b/xen/common/sched_rt.c @@ -3,7 +3,9 @@ * 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 + * Tianyang Chen, 2016, University of Pennsylvania + * Dagaen Golomb, 2016, University of Pennsylvania * * based on the code of credit Scheduler */ @@ -16,6 +18,7 @@ #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 +90,7 @@ #define RTDS_DEFAULT_BUDGET (MICROSECS(4000)) #define UPDATE_LIMIT_SHIFT 10 -#define MAX_SCHEDULE (MILLISECS(1)) + /* * Flags */ @@ -115,6 +118,18 @@ #define RTDS_delayed_runq_add (1<<__RTDS_delayed_runq_add) /* + * The replenishment timer handler needs to check this bit + * to know where a replenished vcpu was, when deciding which + * vcpu should tickle. + * A replenished vcpu should tickle if it was moved from the + * depleted queue to the run queue. + * + Set in burn_budget() if a vcpu has zero budget left. + * + Cleared and checked in the repenishment handler. + */ +#define __RTDS_was_depleted 3 +#define RTDS_was_depleted (1<<__RTDS_was_depleted) + +/* * rt tracing events ("only" 512 available!). Check * include/public/trace.h for more details. */ @@ -142,6 +157,9 @@ 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 +170,9 @@ 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 +180,7 @@ 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 +234,14 @@ 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 +255,18 @@ __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 +327,7 @@ 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 +340,7 @@ 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 +356,13 @@ 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 +427,77 @@ rt_update_deadline(s_time_t now, struct rt_vcpu *svc) return; } +/* + * A helper function that only removes a vcpu from a queue + * and it returns 1 if the vcpu was in front of the list. + */ +static inline int +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 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); +} + +/* + * Removing a vcpu from the replenishment queue could + * re-program the timer for the next replenishment event + * if it was at the front of 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; + + ASSERT( vcpu_on_replq(svc) ); + + if ( deadline_queue_remove(replq, &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); + } + else + stop_timer(repl_timer); + } +} + +/* + * 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; } /* @@ -397,27 +510,62 @@ __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_queue_insert(&__q_elem, svc, &svc->q_elem, runq); else - { list_add(&svc->q_elem, &prv->depletedq); +} + +/* + * 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; + + ASSERT( !vcpu_on_replq(svc) ); + + if ( deadline_queue_insert(&replq_elem, svc, &svc->replq_elem, replq) ) + set_timer(repl_timer, svc->cur_deadline); +} + +/* + * Removes and re-inserts an event to the replenishment queue. + */ +static void +replq_reinsert(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; + + ASSERT( vcpu_on_replq(svc) ); + + if ( deadline_queue_remove(replq, &svc->replq_elem) ) + { + if ( deadline_queue_insert(&replq_elem, svc, &svc->replq_elem, replq) ) + set_timer(repl_timer, svc->cur_deadline); + else + { + struct rt_vcpu *svc_next = replq_elem(replq->next); + set_timer(repl_timer, svc_next->cur_deadline); + } } + else if ( deadline_queue_insert(&replq_elem, svc, &svc->replq_elem, replq) ) + set_timer(repl_timer, svc->cur_deadline); } /* @@ -449,11 +597,18 @@ 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 +628,10 @@ 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 +653,17 @@ 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; } @@ -587,6 +757,7 @@ 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 +781,8 @@ 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 +800,13 @@ 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 +829,10 @@ 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); } @@ -707,7 +888,14 @@ burn_budget(const struct scheduler *ops, struct rt_vcpu *svc, s_time_t now) svc->cur_budget -= delta; if ( svc->cur_budget < 0 ) + { svc->cur_budget = 0; + /* + * Set __RTDS_was_depleted so the replenishment + * handler can let this vcpu tickle if it was refilled. + */ + set_bit(__RTDS_was_depleted, &svc->flags); + } /* TRACE */ { @@ -784,44 +972,6 @@ __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 +990,6 @@ 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 +1016,7 @@ 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 +1029,8 @@ 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->budget; /* invoke the scheduler next time */ } - - ret.time = MIN(snext->budget, MAX_SCHEDULE); /* sched quantum */ ret.task = snext->vcpu; return ret; @@ -903,7 +1051,10 @@ 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 +1159,7 @@ 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 +1181,42 @@ 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 +1227,6 @@ 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 +1238,11 @@ 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 +1300,101 @@ 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 list_head *runq = rt_runq(ops); + struct timer *repl_timer = prv->repl_timer; + struct list_head *iter, *tmp; + struct list_head tmp_replq; + struct rt_vcpu *svc = NULL; + + spin_lock_irqsave(&prv->lock, flags); + + stop_timer(repl_timer); + + /* + * A temperary queue for updated vcpus. + * It is used to tickle. + */ + INIT_LIST_HEAD(&tmp_replq); + + list_for_each_safe(iter, tmp, replq) + { + svc = replq_elem(iter); + + if ( now < svc->cur_deadline ) + break; + + rt_update_deadline(now, svc); + /* + * When a vcpu is replenished, it is moved + * to a temporary queue to tickle. + */ + list_del(&svc->replq_elem); + list_add(&svc->replq_elem, &tmp_replq); + + /* + * If svc is on run queue, we need + * to put it to the correct place since + * its deadline changes. + */ + if( __vcpu_on_q(svc) ) + { + /* put back to runq */ + __q_remove(svc); + __runq_insert(ops, svc); + } + } + + /* Iterate through the list of updated vcpus. */ + list_for_each_safe(iter, tmp, &tmp_replq) + { + struct vcpu* vc; + svc = replq_elem(iter); + vc = svc->vcpu; + + if ( curr_on_cpu(vc->processor) == vc && + ( !list_empty(runq) ) ) + { + /* + * If the vcpu is running, let the head + * of the run queue tickle if it has a + * higher priority. + */ + 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) ) + { + /* Only tickle a vcpu that was depleted. */ + if ( test_and_clear_bit(__RTDS_was_depleted, &svc->flags) ) + runq_tickle(ops, svc); + } + + list_del(&svc->replq_elem); + /* Move it back to the replenishment event queue. */ + deadline_queue_insert(&replq_elem, svc, &svc->replq_elem, replq); + } + + /* + * Use the vcpu that's on the top of the run queue. + * Otherwise 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 const struct scheduler sched_rtds_def = { .name = "SMP RTDS Scheduler", .opt_name = "rtds", -- 1.7.9.5 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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