/* * litmus/sched_cedf.c * * Implementation of the C-EDF scheduling algorithm. * * This implementation is based on G-EDF: * - CPUs are clustered around L2 or L3 caches. * - Clusters topology is automatically detected (this is arch dependent * and is working only on x86 at the moment --- and only with modern * cpus that exports cpuid4 information) * - The plugins _does not_ attempt to put tasks in the right cluster i.e. * the programmer needs to be aware of the topology to place tasks * in the desired cluster * - default clustering is around L2 cache (cache index = 2) * supported clusters are: L1 (private cache: pedf), L2, L3 * * For details on functions, take a look at sched_gsn_edf.c * * This version uses the simple approach and serializes all scheduling * decisions by the use of a queue lock. This is probably not the * best way to do it, but it should suffice for now. */ #include #include #include #include #include #include #include #include #include #include #include /* forward declaration... a funny thing with C ;) */ struct clusterdomain; /* cpu_entry_t - maintain the linked and scheduled state * * A cpu also contains a pointer to the cedf_domain_t cluster * that owns it (struct clusterdomain*) */ typedef struct { int cpu; struct clusterdomain* cluster; /* owning cluster */ struct task_struct* linked; /* only RT tasks */ struct task_struct* scheduled; /* only RT tasks */ atomic_t will_schedule; /* prevent unneeded IPIs */ struct bheap_node* hn; } cpu_entry_t; /* one cpu_entry_t per CPU */ DEFINE_PER_CPU(cpu_entry_t, cedf_cpu_entries); #define set_will_schedule() \ (atomic_set(&__get_cpu_var(cedf_cpu_entries).will_schedule, 1)) #define clear_will_schedule() \ (atomic_set(&__get_cpu_var(cedf_cpu_entries).will_schedule, 0)) #define test_will_schedule(cpu) \ (atomic_read(&per_cpu(cedf_cpu_entries, cpu).will_schedule)) /* * In C-EDF there is a cedf domain _per_ cluster * The number of clusters is dynamically determined accordingly to the * total cpu number and the cluster size */ typedef struct clusterdomain { /* rt_domain for this cluster */ rt_domain_t domain; /* cpus in this cluster */ cpu_entry_t* *cpus; /* map of this cluster cpus */ cpumask_var_t cpu_map; /* the cpus queue themselves according to priority in here */ struct bheap_node *heap_node; struct bheap cpu_heap; /* lock for this cluster */ #define lock domain.ready_lock } cedf_domain_t; /* a cedf_domain per cluster; allocation is done at init/activation time */ cedf_domain_t *cedf; #define remote_cluster(cpu) ((cedf_domain_t *) per_cpu(cedf_cpu_entries, cpu).cluster) #define task_cpu_cluster(task) remote_cluster(get_partition(task)) /* Uncomment WANT_ALL_SCHED_EVENTS if you want to see all scheduling * decisions in the TRACE() log; uncomment VERBOSE_INIT for verbose * information during the initialization of the plugin (e.g., topology) #define WANT_ALL_SCHED_EVENTS */ #define VERBOSE_INIT static int cpu_lower_prio(struct bheap_node *_a, struct bheap_node *_b) { cpu_entry_t *a, *b; a = _a->value; b = _b->value; /* Note that a and b are inverted: we want the lowest-priority CPU at * the top of the heap. */ return edf_higher_prio(b->linked, a->linked); } /* update_cpu_position - Move the cpu entry to the correct place to maintain * order in the cpu queue. Caller must hold cedf lock. */ static void update_cpu_position(cpu_entry_t *entry) { cedf_domain_t *cluster = entry->cluster; if (likely(bheap_node_in_heap(entry->hn))) bheap_delete(cpu_lower_prio, &cluster->cpu_heap, entry->hn); bheap_insert(cpu_lower_prio, &cluster->cpu_heap, entry->hn); } /* caller must hold cedf lock */ static cpu_entry_t* lowest_prio_cpu(cedf_domain_t *cluster) { struct bheap_node* hn; hn = bheap_peek(cpu_lower_prio, &cluster->cpu_heap); return hn->value; } /* link_task_to_cpu - Update the link of a CPU. * Handles the case where the to-be-linked task is already * scheduled on a different CPU. */ static noinline void link_task_to_cpu(struct task_struct* linked, cpu_entry_t *entry) { cpu_entry_t *sched; struct task_struct* tmp; int on_cpu; BUG_ON(linked && !is_realtime(linked)); /* Currently linked task is set to be unlinked. */ if (entry->linked) { entry->linked->rt_param.linked_on = NO_CPU; } /* Link new task to CPU. */ if (linked) { set_rt_flags(linked, RT_F_RUNNING); /* handle task is already scheduled somewhere! */ on_cpu = linked->rt_param.scheduled_on; if (on_cpu != NO_CPU) { sched = &per_cpu(cedf_cpu_entries, on_cpu); /* this should only happen if not linked already */ BUG_ON(sched->linked == linked); /* If we are already scheduled on the CPU to which we * wanted to link, we don't need to do the swap -- * we just link ourselves to the CPU and depend on * the caller to get things right. */ if (entry != sched) { TRACE_TASK(linked, "already scheduled on %d, updating link.\n", sched->cpu); tmp = sched->linked; linked->rt_param.linked_on = sched->cpu; sched->linked = linked; update_cpu_position(sched); linked = tmp; } } if (linked) /* might be NULL due to swap */ linked->rt_param.linked_on = entry->cpu; } entry->linked = linked; #ifdef WANT_ALL_SCHED_EVENTS if (linked) TRACE_TASK(linked, "linked to %d.\n", entry->cpu); else TRACE("NULL linked to %d.\n", entry->cpu); #endif update_cpu_position(entry); } /* unlink - Make sure a task is not linked any longer to an entry * where it was linked before. Must hold cedf_lock. */ static noinline void unlink(struct task_struct* t) { cpu_entry_t *entry; if (unlikely(!t)) { TRACE_BUG_ON(!t); return; } if (t->rt_param.linked_on != NO_CPU) { /* unlink */ entry = &per_cpu(cedf_cpu_entries, t->rt_param.linked_on); t->rt_param.linked_on = NO_CPU; link_task_to_cpu(NULL, entry); } else if (is_queued(t)) { /* This is an interesting situation: t is scheduled, * but was just recently unlinked. It cannot be * linked anywhere else (because then it would have * been relinked to this CPU), thus it must be in some * queue. We must remove it from the list in this * case. * * in C-EDF case is should be somewhere in the queue for * its domain, therefore and we can get the domain using * task_cpu_cluster */ remove(&(task_cpu_cluster(t))->domain, t); } } /* preempt - force a CPU to reschedule */ static void preempt(cpu_entry_t *entry) { preempt_if_preemptable(entry->scheduled, entry->cpu); } /* requeue - Put an unlinked task into gsn-edf domain. * Caller must hold cedf_lock. */ static noinline void requeue(struct task_struct* task) { cedf_domain_t *cluster = task_cpu_cluster(task); BUG_ON(!task); /* sanity check before insertion */ BUG_ON(is_queued(task)); if (is_released(task, litmus_clock())) __add_ready(&cluster->domain, task); else { /* it has got to wait */ add_release(&cluster->domain, task); } } /* check for any necessary preemptions */ static void check_for_preemptions(cedf_domain_t *cluster) { struct task_struct *task; cpu_entry_t* last; for(last = lowest_prio_cpu(cluster); edf_preemption_needed(&cluster->domain, last->linked); last = lowest_prio_cpu(cluster)) { /* preemption necessary */ task = __take_ready(&cluster->domain); TRACE("check_for_preemptions: attempting to link task %d to %d\n", task->pid, last->cpu); if (last->linked) requeue(last->linked); link_task_to_cpu(task, last); preempt(last); } } /* cedf_job_arrival: task is either resumed or released */ static noinline void cedf_job_arrival(struct task_struct* task) { cedf_domain_t *cluster = task_cpu_cluster(task); BUG_ON(!task); requeue(task); check_for_preemptions(cluster); } static void cedf_release_jobs(rt_domain_t* rt, struct bheap* tasks) { cedf_domain_t* cluster = container_of(rt, cedf_domain_t, domain); unsigned long flags; raw_spin_lock_irqsave(&cluster->lock, flags); __merge_ready(&cluster->domain, tasks); check_for_preemptions(cluster); raw_spin_unlock_irqrestore(&cluster->lock, flags); } /* caller holds cedf_lock */ static noinline void job_completion(struct task_struct *t, int forced) { BUG_ON(!t); sched_trace_task_completion(t, forced); TRACE_TASK(t, "job_completion().\n"); /* set flags */ set_rt_flags(t, RT_F_SLEEP); /* prepare for next period */ prepare_for_next_period(t); if (is_released(t, litmus_clock())) sched_trace_task_release(t); /* unlink */ unlink(t); /* requeue * But don't requeue a blocking task. */ if (is_running(t)) cedf_job_arrival(t); } /* cedf_tick - this function is called for every local timer * interrupt. * * checks whether the current task has expired and checks * whether we need to preempt it if it has not expired */ static void cedf_tick(struct task_struct* t) { if (is_realtime(t) && budget_enforced(t) && budget_exhausted(t)) { if (!is_np(t)) { /* np tasks will be preempted when they become * preemptable again */ set_tsk_need_resched(t); set_will_schedule(); TRACE("cedf_scheduler_tick: " "%d is preemptable " " => FORCE_RESCHED\n", t->pid); } else if (is_user_np(t)) { TRACE("cedf_scheduler_tick: " "%d is non-preemptable, " "preemption delayed.\n", t->pid); request_exit_np(t); } } } /* Getting schedule() right is a bit tricky. schedule() may not make any * assumptions on the state of the current task since it may be called for a * number of reasons. The reasons include a scheduler_tick() determined that it * was necessary, because sys_exit_np() was called, because some Linux * subsystem determined so, or even (in the worst case) because there is a bug * hidden somewhere. Thus, we must take extreme care to determine what the * current state is. * * The CPU could currently be scheduling a task (or not), be linked (or not). * * The following assertions for the scheduled task could hold: * * - !is_running(scheduled) // the job blocks * - scheduled->timeslice == 0 // the job completed (forcefully) * - get_rt_flag() == RT_F_SLEEP // the job completed (by syscall) * - linked != scheduled // we need to reschedule (for any reason) * - is_np(scheduled) // rescheduling must be delayed, * sys_exit_np must be requested * * Any of these can occur together. */ static struct task_struct* cedf_schedule(struct task_struct * prev) { cpu_entry_t* entry = &__get_cpu_var(cedf_cpu_entries); cedf_domain_t *cluster = entry->cluster; int out_of_time, sleep, preempt, np, exists, blocks; struct task_struct* next = NULL; raw_spin_lock(&cluster->lock); clear_will_schedule(); /* sanity checking */ BUG_ON(entry->scheduled && entry->scheduled != prev); BUG_ON(entry->scheduled && !is_realtime(prev)); BUG_ON(is_realtime(prev) && !entry->scheduled); /* (0) Determine state */ exists = entry->scheduled != NULL; blocks = exists && !is_running(entry->scheduled); out_of_time = exists && budget_enforced(entry->scheduled) && budget_exhausted(entry->scheduled); np = exists && is_np(entry->scheduled); sleep = exists && get_rt_flags(entry->scheduled) == RT_F_SLEEP; preempt = entry->scheduled != entry->linked; #ifdef WANT_ALL_SCHED_EVENTS TRACE_TASK(prev, "invoked cedf_schedule.\n"); #endif if (exists) TRACE_TASK(prev, "blocks:%d out_of_time:%d np:%d sleep:%d preempt:%d " "state:%d sig:%d\n", blocks, out_of_time, np, sleep, preempt, prev->state, signal_pending(prev)); if (entry->linked && preempt) TRACE_TASK(prev, "will be preempted by %s/%d\n", entry->linked->comm, entry->linked->pid); /* If a task blocks we have no choice but to reschedule. */ if (blocks) unlink(entry->scheduled); /* Request a sys_exit_np() call if we would like to preempt but cannot. * We need to make sure to update the link structure anyway in case * that we are still linked. Multiple calls to request_exit_np() don't * hurt. */ if (np && (out_of_time || preempt || sleep)) { unlink(entry->scheduled); request_exit_np(entry->scheduled); } /* Any task that is preemptable and either exhausts its execution * budget or wants to sleep completes. We may have to reschedule after * this. Don't do a job completion if we block (can't have timers running * for blocked jobs). Preemption go first for the same reason. */ if (!np && (out_of_time || sleep) && !blocks && !preempt) job_completion(entry->scheduled, !sleep); /* Link pending task if we became unlinked. */ if (!entry->linked) link_task_to_cpu(__take_ready(&cluster->domain), entry); /* The final scheduling decision. Do we need to switch for some reason? * If linked is different from scheduled, then select linked as next. */ if ((!np || blocks) && entry->linked != entry->scheduled) { /* Schedule a linked job? */ if (entry->linked) { entry->linked->rt_param.scheduled_on = entry->cpu; next = entry->linked; } if (entry->scheduled) { /* not gonna be scheduled soon */ entry->scheduled->rt_param.scheduled_on = NO_CPU; TRACE_TASK(entry->scheduled, "scheduled_on = NO_CPU\n"); } } else /* Only override Linux scheduler if we have a real-time task * scheduled that needs to continue. */ if (exists) next = prev; raw_spin_unlock(&cluster->lock); #ifdef WANT_ALL_SCHED_EVENTS TRACE("cedf_lock released, next=0x%p\n", next); if (next) TRACE_TASK(next, "scheduled at %llu\n", litmus_clock()); else if (exists && !next) TRACE("becomes idle at %llu.\n", litmus_clock()); #endif return next; } /* _finish_switch - we just finished the switch away from prev */ static void cedf_finish_switch(struct task_struct *prev) { cpu_entry_t* entry = &__get_cpu_var(cedf_cpu_entries); entry->scheduled = is_realtime(current) ? current : NULL; #ifdef WANT_ALL_SCHED_EVENTS TRACE_TASK(prev, "switched away from\n"); #endif } /* Prepare a task for running in RT mode */ static void cedf_task_new(struct task_struct * t, int on_rq, int running) { unsigned long flags; cpu_entry_t* entry; cedf_domain_t* cluster; TRACE("gsn edf: task new %d\n", t->pid); /* the cluster doesn't change even if t is running */ cluster = task_cpu_cluster(t); raw_spin_lock_irqsave(&cluster->domain.ready_lock, flags); /* setup job params */ release_at(t, litmus_clock()); if (running) { entry = &per_cpu(cedf_cpu_entries, task_cpu(t)); BUG_ON(entry->scheduled); entry->scheduled = t; tsk_rt(t)->scheduled_on = task_cpu(t); } else { t->rt_param.scheduled_on = NO_CPU; } t->rt_param.linked_on = NO_CPU; cedf_job_arrival(t); raw_spin_unlock_irqrestore(&(cluster->domain.ready_lock), flags); } static void cedf_task_wake_up(struct task_struct *task) { unsigned long flags; lt_t now; cedf_domain_t *cluster; TRACE_TASK(task, "wake_up at %llu\n", litmus_clock()); cluster = task_cpu_cluster(task); raw_spin_lock_irqsave(&cluster->lock, flags); /* We need to take suspensions because of semaphores into * account! If a job resumes after being suspended due to acquiring * a semaphore, it should never be treated as a new job release. */ if (get_rt_flags(task) == RT_F_EXIT_SEM) { set_rt_flags(task, RT_F_RUNNING); } else { now = litmus_clock(); if (is_tardy(task, now)) { /* new sporadic release */ release_at(task, now); sched_trace_task_release(task); } else { if (task->rt.time_slice) { /* came back in time before deadline */ set_rt_flags(task, RT_F_RUNNING); } } } cedf_job_arrival(task); raw_spin_unlock_irqrestore(&cluster->lock, flags); } static void cedf_task_block(struct task_struct *t) { unsigned long flags; cedf_domain_t *cluster; TRACE_TASK(t, "block at %llu\n", litmus_clock()); cluster = task_cpu_cluster(t); /* unlink if necessary */ raw_spin_lock_irqsave(&cluster->lock, flags); unlink(t); raw_spin_unlock_irqrestore(&cluster->lock, flags); BUG_ON(!is_realtime(t)); } static void cedf_task_exit(struct task_struct * t) { unsigned long flags; cedf_domain_t *cluster = task_cpu_cluster(t); /* unlink if necessary */ raw_spin_lock_irqsave(&cluster->lock, flags); unlink(t); if (tsk_rt(t)->scheduled_on != NO_CPU) { cluster->cpus[tsk_rt(t)->scheduled_on]->scheduled = NULL; tsk_rt(t)->scheduled_on = NO_CPU; } raw_spin_unlock_irqrestore(&cluster->lock, flags); BUG_ON(!is_realtime(t)); TRACE_TASK(t, "RIP\n"); } static long cedf_admit_task(struct task_struct* tsk) { return task_cpu(tsk) == tsk->rt_param.task_params.cpu ? 0 : -EINVAL; } /* total number of cluster */ static int num_clusters; /* we do not support cluster of different sizes */ static unsigned int cluster_size; #ifdef VERBOSE_INIT static void print_cluster_topology(cpumask_var_t mask, int cpu) { int chk; char buf[255]; chk = cpulist_scnprintf(buf, 254, mask); buf[chk] = '\0'; printk(KERN_INFO "CPU = %d, shared cpu(s) = %s\n", cpu, buf); } #endif static int clusters_allocated = 0; static void cleanup_cedf(void) { int i; if (clusters_allocated) { for (i = 0; i < num_clusters; i++) { kfree(cedf[i].cpus); kfree(cedf[i].heap_node); free_cpumask_var(cedf[i].cpu_map); } kfree(cedf); } } static long cedf_activate_plugin(void) { int i, j, cpu, ccpu, cpu_count; cpu_entry_t *entry; cpumask_var_t mask; int chk = 0; /* de-allocate old clusters, if any */ cleanup_cedf(); printk(KERN_INFO "C-EDF: Activate Plugin, cache index = %d\n", cluster_cache_index); /* need to get cluster_size first */ if(!zalloc_cpumask_var(&mask, GFP_ATOMIC)) return -ENOMEM; chk = get_shared_cpu_map(mask, 0, cluster_cache_index); if (chk) { /* if chk != 0 then it is the max allowed index */ printk(KERN_INFO "C-EDF: Cannot support cache index = %d\n", cluster_cache_index); printk(KERN_INFO "C-EDF: Using cache index = %d\n", chk); cluster_cache_index = chk; } cluster_size = cpumask_weight(mask); if ((num_online_cpus() % cluster_size) != 0) { /* this can't be right, some cpus are left out */ printk(KERN_ERR "C-EDF: Trying to group %d cpus in %d!\n", num_online_cpus(), cluster_size); return -1; } num_clusters = num_online_cpus() / cluster_size; printk(KERN_INFO "C-EDF: %d cluster(s) of size = %d\n", num_clusters, cluster_size); /* initialize clusters */ cedf = kmalloc(num_clusters * sizeof(cedf_domain_t), GFP_ATOMIC); for (i = 0; i < num_clusters; i++) { cedf[i].cpus = kmalloc(cluster_size * sizeof(cpu_entry_t), GFP_ATOMIC); cedf[i].heap_node = kmalloc( cluster_size * sizeof(struct bheap_node), GFP_ATOMIC); bheap_init(&(cedf[i].cpu_heap)); edf_domain_init(&(cedf[i].domain), NULL, cedf_release_jobs); if(!zalloc_cpumask_var(&cedf[i].cpu_map, GFP_ATOMIC)) return -ENOMEM; } /* cycle through cluster and add cpus to them */ for (i = 0; i < num_clusters; i++) { for_each_online_cpu(cpu) { /* check if the cpu is already in a cluster */ for (j = 0; j < num_clusters; j++) if (cpumask_test_cpu(cpu, cedf[j].cpu_map)) break; /* if it is in a cluster go to next cpu */ if (cpumask_test_cpu(cpu, cedf[j].cpu_map)) continue; /* this cpu isn't in any cluster */ /* get the shared cpus */ get_shared_cpu_map(mask, cpu, cluster_cache_index); cpumask_copy(cedf[i].cpu_map, mask); #ifdef VERBOSE_INIT print_cluster_topology(mask, cpu); #endif /* add cpus to current cluster and init cpu_entry_t */ cpu_count = 0; for_each_cpu(ccpu, cedf[i].cpu_map) { entry = &per_cpu(cedf_cpu_entries, ccpu); cedf[i].cpus[cpu_count] = entry; atomic_set(&entry->will_schedule, 0); entry->cpu = ccpu; entry->cluster = &cedf[i]; entry->hn = &(cedf[i].heap_node[cpu_count]); bheap_node_init(&entry->hn, entry); cpu_count++; entry->linked = NULL; entry->scheduled = NULL; update_cpu_position(entry); } /* done with this cluster */ break; } } free_cpumask_var(mask); clusters_allocated = 1; return 0; } /* Plugin object */ static struct sched_plugin cedf_plugin __cacheline_aligned_in_smp = { .plugin_name = "C-EDF", .finish_switch = cedf_finish_switch, .tick = cedf_tick, .task_new = cedf_task_new, .complete_job = complete_job, .task_exit = cedf_task_exit, .schedule = cedf_schedule, .task_wake_up = cedf_task_wake_up, .task_block = cedf_task_block, .admit_task = cedf_admit_task, .activate_plugin = cedf_activate_plugin, }; static int __init init_cedf(void) { return register_sched_plugin(&cedf_plugin); } static void clean_cedf(void) { cleanup_cedf(); } module_init(init_cedf); module_exit(clean_cedf);