set_timer: Start timer when runnable thread count is bigger than one

Change-Id: Ie32799fff2936ffc057f166db5681edccdbf5920

kernel/include/process.h

@@ -837,7 +837,7 @@ void process_unlock(struct process *proc, struct mcs_rwlock_node_irqsave *lock);
 void chain_process(struct process *);
 void chain_thread(struct thread *);
 void proc_init(void);
-void set_timer(void);
+void set_timer(int runq_locked);
 struct sig_pending *hassigpending(struct thread *thread);
 
 void release_fp_regs(struct thread *proc);

kernel/process.c

@@ -3063,13 +3063,26 @@ ack:
 	ihk_mc_spinlock_unlock(&cur_v->migq_lock, irqstate);
 }
 
-void
-set_timer()
+void set_timer(int runq_locked)
 {
 	struct cpu_local_var *v = get_this_cpu_local_var();
+	struct thread *thread;
+	int num_running = 0;
+	unsigned long irqstate;
+
+	if (!runq_locked) {
+		irqstate = ihk_mc_spinlock_lock(&(v->runq_lock));
+	}
+
+	list_for_each_entry(thread, &v->runq, sched_list) {
+		if (thread->status != PS_RUNNING) {
+			continue;
+		}
+		num_running++;
+	}
 
 	/* Toggle timesharing if CPU core is oversubscribed */
-	if (v->runq_len > 1 || v->current->itimer_enabled) {
+	if (num_running > 1 || v->current->itimer_enabled) {
 		if (!cpu_local_var(timer_enabled)) {
 			lapic_timer_enable(/*10000000*/1000000);
 			cpu_local_var(timer_enabled) = 1;
@@ -3081,6 +3094,10 @@ set_timer()
 			cpu_local_var(timer_enabled) = 0;
 		}
 	}
+
+	if (!runq_locked) {
+		ihk_mc_spinlock_unlock(&(v->runq_lock), irqstate);
+	}
 }
 
 /*
@@ -3222,7 +3239,7 @@ void schedule(void)
 		reset_cputime();
 	}
 
-	set_timer();
+	set_timer(1);
 
 	if (switch_ctx) {
 		dkprintf("schedule: %d => %d \n",

kernel/syscall.c

@@ -7050,7 +7050,7 @@ SYSCALL_DECLARE(setitimer)
 			timer_start = 0;
 	}
 	thread->itimer_enabled = timer_start;
-	set_timer();
+	set_timer(0);
 	return 0;
 }
 
@@ -9499,7 +9499,7 @@ set_cputime(int mode)
 			   thread->itimer_prof.it_value.tv_sec == 0 &&
 			   thread->itimer_prof.it_value.tv_usec == 0){
 				thread->itimer_enabled = 0;
-				set_timer();
+				set_timer(0);
 			}
 		}
 	}