Add C-EDF Plugin2010.1

Improved C-EDF plugin. C-EDF now supports different cluster sizes (based
on L2 and L3 cache sharing) and supports dynamic changes of cluster size
(this requires reloading the plugin).

5 files changed, 832 insertions, 0 deletions

diff --git a/include/litmus/sched_plugin.h b/include/litmus/sched_plugin.h
index 2d856d587041..9c1c9f28ba79 100644
--- a/include/litmus/sched_plugin.h
+++ b/include/litmus/sched_plugin.h
@@ -133,6 +133,9 @@ struct sched_plugin {
 
 extern struct sched_plugin *litmus;
 
+/* cluster size: cache_index = 2 L2, cache_index = 3 L3 */
+extern int cluster_cache_index;
+
 int register_sched_plugin(struct sched_plugin* plugin);
 struct sched_plugin* find_sched_plugin(const char* name);
 int print_sched_plugins(char* buf, int max);
diff --git a/litmus/Makefile b/litmus/Makefile
index ff4eb8a7b6c4..0cc33e8bee51 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -14,6 +14,7 @@ obj-y     = sched_plugin.o litmus.o \
             ctrldev.o \
             sched_gsn_edf.o \
             sched_psn_edf.o \
+            sched_cedf.o \
             sched_pfair.o
 
 obj-$(CONFIG_FEATHER_TRACE) += ft_event.o ftdev.o
diff --git a/litmus/litmus.c b/litmus/litmus.c
index 3ef2df8ffb50..e43596a5104c 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -566,6 +566,55 @@ static int proc_write_curr(struct file *file,
         return len;
 }
 
+static int proc_read_cluster_size(char *page, char **start,
+                          off_t off, int count,
+                          int *eof, void *data)
+{
+        int len;
+        if (cluster_cache_index == 2)
+                len = snprintf(page, PAGE_SIZE, "L2\n");
+        else if (cluster_cache_index == 3)
+                len = snprintf(page, PAGE_SIZE, "L3\n");
+        else /* (cluster_cache_index == 1) */
+                len = snprintf(page, PAGE_SIZE, "L1\n");
+
+        return len;
+}
+
+static int proc_write_cluster_size(struct file *file,
+                           const char *buffer,
+                           unsigned long count,
+                           void *data)
+{
+        int len;
+        /* L2, L3 */
+        char cache_name[33];
+
+        if(count > 32)
+                len = 32;
+        else
+                len = count;
+
+        if(copy_from_user(cache_name, buffer, len))
+                return -EFAULT;
+
+        cache_name[len] = '\0';
+        /* chomp name */
+        if (len > 1 && cache_name[len - 1] == '\n')
+                cache_name[len - 1] = '\0';
+
+        /* do a quick and dirty comparison to find the cluster size */
+        if (!strcmp(cache_name, "L2"))
+                cluster_cache_index = 2;
+        else if (!strcmp(cache_name, "L3"))
+                cluster_cache_index = 3;
+        else if (!strcmp(cache_name, "L1"))
+                cluster_cache_index = 1;
+        else
+                printk(KERN_INFO "Cluster '%s' is unknown.\n", cache_name);
+
+        return len;
+}
 
 static int proc_read_release_master(char *page, char **start,
                                     off_t off, int count,
@@ -621,6 +670,7 @@ static struct proc_dir_entry *litmus_dir = NULL,
         *curr_file = NULL,
         *stat_file = NULL,
         *plugs_file = NULL,
+        *clus_cache_idx_file = NULL,
         *release_master_file = NULL;
 
 static int __init init_litmus_proc(void)
@@ -651,6 +701,16 @@ static int __init init_litmus_proc(void)
         release_master_file->read_proc = proc_read_release_master;
         release_master_file->write_proc  = proc_write_release_master;
 
+        clus_cache_idx_file = create_proc_entry("cluster_cache",
+                                                0644, litmus_dir);
+        if (!clus_cache_idx_file) {
+                printk(KERN_ERR "Could not allocate cluster_cache "
+                       "procfs entry.\n");
+                return -ENOMEM;
+        }
+        clus_cache_idx_file->read_proc = proc_read_cluster_size;
+        clus_cache_idx_file->write_proc = proc_write_cluster_size;
+
         stat_file = create_proc_read_entry("stats", 0444, litmus_dir,
                                            proc_read_stats, NULL);
 
@@ -668,6 +728,10 @@ static void exit_litmus_proc(void)
                 remove_proc_entry("stats", litmus_dir);
         if (curr_file)
                 remove_proc_entry("active_plugin", litmus_dir);
+        if (clus_cache_idx_file)
+                remove_proc_entry("cluster_cache", litmus_dir);
+        if (release_master_file)
+                remove_proc_entry("release_master", litmus_dir);
         if (litmus_dir)
                 remove_proc_entry("litmus", NULL);
 }
diff --git a/litmus/sched_cedf.c b/litmus/sched_cedf.c
new file mode 100644
index 000000000000..da44b451c9ad
--- /dev/null
+++ b/litmus/sched_cedf.c
@@ -0,0 +1,756 @@
+/*
+ * 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 <linux/spinlock.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+
+#include <litmus/litmus.h>
+#include <litmus/jobs.h>
+#include <litmus/sched_plugin.h>
+#include <litmus/edf_common.h>
+#include <litmus/sched_trace.h>
+
+#include <litmus/bheap.h>
+
+#include <linux/module.h>
+
+/* 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;
+
+        spin_lock_irqsave(&cluster->lock, flags);
+
+        __merge_ready(&cluster->domain, tasks);
+        check_for_preemptions(cluster);
+
+        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_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;
+
+        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_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;
+
+        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);
+
+        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);
+        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);
+
+        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);
+        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 */
+        spin_lock_irqsave(&cluster->lock, flags);
+        unlink(t);
+        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 */
+        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;
+        }
+        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);
diff --git a/litmus/sched_plugin.c b/litmus/sched_plugin.c
index bc7c0e93fb18..3767b30e610a 100644
--- a/litmus/sched_plugin.c
+++ b/litmus/sched_plugin.c
@@ -171,6 +171,14 @@ struct sched_plugin linux_sched_plugin = {
 };
 
 /*
+ * The cluster size is needed in C-EDF: it makes sense only to cluster
+ * around L2 or L3, so if cluster_cache_index = 2 (default) we cluster
+ * all the CPUs that shares a L2 cache, while cluster_cache_index = 3
+ * we cluster all CPs that shares a L3 cache
+ */
+int cluster_cache_index = 2;
+
+/*
  *      The reference to current plugin that is used to schedule tasks within
  *      the system. It stores references to actual function implementations
  *      Should be initialized by calling "init_***_plugin()"