From 670b3f850c93dde7257d88fc7b688d95d5e1e18c Mon Sep 17 00:00:00 2001
From: Stefan Lankes <lankes@lfbs.rwth-aachen.de>
Date: Thu, 22 Sep 2011 09:48:40 +0200
Subject: [PATCH] add first version of our load balancer

---
 kernel/tasks.c | 41 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/kernel/tasks.c b/kernel/tasks.c
index bb59b3b0..b7ba3672 100644
--- a/kernel/tasks.c
+++ b/kernel/tasks.c
@@ -1115,9 +1115,33 @@ void update_load(void)
 
 #if MAX_CORES > 1
 extern atomic_int32_t cpu_online;
+#endif
 
+void dump_load(void)
+{
+	uint32_t i;
+#if MAX_CORES > 1
+	uint32_t ncores = atomic_int32_read(&cpu_online);
+#else
+	uint32_t ncores = 1;
+#endif
+
+	for(i=0; i<ncores; i++)
+	{
+		kprintf("Load average of core %u: %u.%u, %u.%u, %u.%u\n",
+				i, runqueues[i].load[0] >> FSHIFT,
+				((runqueues[i].load[0] & ((1 << FSHIFT) - 1)) * 100) / (1 << FSHIFT),
+				runqueues[i].load[1] >> FSHIFT,
+				((runqueues[i].load[1] & ((1 << FSHIFT) - 1)) * 100) / (1 << FSHIFT),
+				runqueues[i].load[2] >> FSHIFT,
+				((runqueues[i].load[2] & ((1 << FSHIFT) - 1)) * 100) / (1 << FSHIFT));
+	}
+}
+
+#if MAX_CORES > 1
 void load_balancing(void)
 {
+#if 1
 	uint32_t i, core_id = CORE_ID;
 	uint32_t prio;
 	task_t* task;
@@ -1133,18 +1157,19 @@ void load_balancing(void)
 			kprintf("Try to steal a task from core %u (load %u) to %u (load %u)\n", i, runqueues[i].load[0], core_id, runqueues[core_id].load[0]);
 			kprintf("Task on core %u: %u, core %u, %u\n", i, runqueues[i].nr_tasks, core_id, runqueues[i].nr_tasks);
 
-			prio = msb(runqueues[i].prio_bitmap);
+			prio = lsb(runqueues[i].prio_bitmap);
 			if (prio < sizeof(size_t)*8) {
 				// steal a ready task
 				task = runqueues[i].queue[prio-1].last;
-				kprintf("Try to steal a ready task %d\n", task->id);
+				kprintf("Try to steal a ready task %d with prio %u\n", task->id, prio);
 
 				// remove last element from queue i
 				if (task->prev)
 					task->prev->next = NULL;
-				runqueues[i].queue[prio-1].last = task->prev;
-				if (!runqueues[i].queue[prio-1].last)
-					runqueues[i].queue[prio-1].first = NULL;
+				if (runqueues[i].queue[prio-1].first == task) {
+					runqueues[i].queue[prio-1].first = runqueues[i].queue[prio-1].last = NULL;
+					runqueues[i].prio_bitmap &= ~(1 << prio);
+				} else runqueues[i].queue[prio-1].last = task->prev;
 
 				// add task at the end of queue core_id
 				if (!runqueues[core_id].queue[prio-1].last) {
@@ -1156,12 +1181,13 @@ void load_balancing(void)
 					runqueues[core_id].queue[prio-1].last = task;
 					task->next = NULL;
 				}
+				runqueues[core_id].prio_bitmap |= (1 << prio);
 
 				// update task counters
 				runqueues[core_id].nr_tasks++;
 				runqueues[i].nr_tasks--;
 				runqueues[core_id].balance_counter = TIMER_FREQ/2;
-			} /*else {
+			} else {
 				task_t* tmp;
 
 				// steal a blocked task
@@ -1207,12 +1233,13 @@ void load_balancing(void)
 				runqueues[core_id].nr_tasks++;
 				runqueues[i].nr_tasks--;
 				runqueues[core_id].balance_counter = TIMER_FREQ/2;
-			}*/
+			}
 		}
 no_task_found:
 		spinlock_irqsave_unlock(&runqueues[i].lock);
 	}
 	spinlock_irqsave_unlock(&runqueues[core_id].lock);
+#endif
 }
 #endif