Add kernel argument to turn on/off time sharing

Add "-T 0" to mcreboot.sh if you want to turn off time sharing.  When
it's turned off, McKernel doesn't activate interval timer when the
length of per-CPU run-queue is larger than one.

Change-Id: I2cedc1b30a9cd9a0f4608a32ecec0a0d58c6225e

kernel/include/process.h

@@ -280,6 +280,7 @@ extern struct list_head	resource_set_list;
 extern mcs_rwlock_lock_t	resource_set_lock;
 extern int idle_halt;
 extern int allow_oversubscribe;
+extern int time_sharing;
 extern ihk_spinlock_t runq_reservation_lock; /* mutex for cpuid reservation (clv->runq_reserved) */
 
 struct process_hash {

kernel/init.c

@@ -168,6 +168,12 @@ static void parse_kargs(void)
 	if (ptr) {
 		allow_oversubscribe = 1;
 	}
+
+	/* time_sharing option */
+	ptr = find_command_line("time_sharing");
+	if (ptr) {
+		time_sharing = 1;
+	}
 }
 
 extern void ihk_mc_get_boot_time(unsigned long *tv_sec, unsigned long *tv_nsec);

kernel/process.c

@@ -91,6 +91,7 @@ ihk_spinlock_t runq_reservation_lock;
 
 int idle_halt = 0;
 int allow_oversubscribe = 0;
+int time_sharing = 0;
 
 void
 init_process(struct process *proc, struct process *parent)
@@ -3100,6 +3101,10 @@ void set_timer(int runq_locked)
 	int num_running = 0;
 	unsigned long irqstate;
 
+	if (!time_sharing) {
+		return;
+	}
+
 	if (!runq_locked) {
 		irqstate = ihk_mc_spinlock_lock(&(v->runq_lock));
 	}