implement recent_cpu

src/devices/timer.c

@@ -199,6 +199,10 @@ static void
 timer_interrupt (struct intr_frame *args UNUSED)
 {
   ticks++;
+  if (ticks % TIMER_FREQ == 0)
+  {
+    calculate_recent_cpu ();
+  }
   for (struct list_elem *e = list_begin (&sleeping_threads);
        e != list_end (&sleeping_threads); e = list_next (e))
     {
@@ -208,6 +212,7 @@ timer_interrupt (struct intr_frame *args UNUSED)
       else
         break;
     }
+  thread_increment_recent_cpu ();
   thread_tick ();
 }
 

src/threads/thread.c

@@ -65,7 +65,7 @@ static void kernel_thread (thread_func *, void *aux);
 static void idle (void *aux UNUSED);
 static struct thread *running_thread (void);
 static struct thread *next_thread_to_run (void);
-static void init_thread (struct thread *, const char *name, int priority);
+static void init_thread (struct thread *, const char *name, int priority, fp32_t recent_cpu);
 static bool is_thread (struct thread *) UNUSED;
 static void *alloc_frame (struct thread *, size_t size);
 static void schedule (void);
@@ -96,7 +96,8 @@ thread_init (void)
 
   /* Set up a thread structure for the running thread. */
   initial_thread = running_thread ();
-  init_thread (initial_thread, "main", PRI_DEFAULT);
+  fp32_t initial_thread_recent_cpu = { 0 };
+  init_thread (initial_thread, "main", PRI_DEFAULT, initial_thread_recent_cpu);
   initial_thread->status = THREAD_RUNNING;
   initial_thread->tid = allocate_tid ();
 }
@@ -193,7 +194,8 @@ thread_create (const char *name, int priority,
     return TID_ERROR;
 
   /* Initialize thread. */
-  init_thread (t, name, priority);
+  fp32_t parent_recent_cpu = thread_current ()->recent_cpu;
+  init_thread (t, name, priority, parent_recent_cpu);
   tid = t->tid = allocate_tid ();
 
   /* Prepare thread for first run by initializing its stack.
@@ -373,6 +375,30 @@ calculate_priority (void)
 	return 0;
 }
 
+void
+calculate_recent_cpu (void)
+{
+  struct thread *t = thread_current ();
+  fp32_t curr_recent_cpu = t->recent_cpu;
+  fp32_t curr_load_avg = fp_mul_int(thread_get_load_avg (), 2);
+  fp32_t recent_cpu_coeff = fp_div(curr_load_avg, fp_add_int(curr_load_avg, 1));
+  fp32_t new_recent_cpu = fp_add_int(fp_mul(recent_cpu_coeff, curr_recent_cpu), thread_get_nice ());
+  t->recent_cpu = new_recent_cpu;
+}
+
+void
+thread_increment_recent_cpu (void)
+{
+  struct thread *t = thread_current ();
+  if (t == idle_thread)
+  {
+    return;
+  }
+  fp32_t old_recent_cpu = t->recent_cpu;
+  old_recent_cpu.raw = old_recent_cpu.raw + 1;
+  t->recent_cpu = old_recent_cpu;
+}
+
 /* Sets the current thread's nice value to NICE. */
 void
 thread_set_nice (int nice)
@@ -476,7 +502,7 @@ is_thread (struct thread *t)
 /* Does basic initialization of T as a blocked thread named
    NAME. */
 static void
-init_thread (struct thread *t, const char *name, int priority)
+init_thread (struct thread *t, const char *name, int priority, fp32_t recent_cpu)
 {
   enum intr_level old_level;
 
@@ -490,6 +516,7 @@ init_thread (struct thread *t, const char *name, int priority)
   t->stack = (uint8_t *) t + PGSIZE;
   t->priority = priority;
   t->magic = THREAD_MAGIC;
+  t->recent_cpu = recent_cpu;
 
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);

src/threads/thread.h

@@ -96,7 +96,7 @@ struct thread
 
     /* MLFQS items */
     int nice;                           /* Nice value for this thread */
-    fp32_t recent_cpu; /* Amount of time this process received */
+    fp32_t recent_cpu;                  /* Amount of time this process received */
 
 #ifdef USERPROG
     /* Owned by userprog/process.c. */