-#include "timer.h"
-#include "debug.h"
-#include "interrupt.h"
-#include "io.h"
+#include "devices/timer.h"
+#include <debug.h>
+#include <inttypes.h>
+#include <round.h>
+#include <stdio.h>
+#include "threads/interrupt.h"
+#include "threads/io.h"
+#include "threads/thread.h"
+/* See [8254] for hardware details of the 8254 timer chip. */
+
#if TIMER_FREQ < 19
#error 8254 timer requires TIMER_FREQ >= 19
#endif
+#if TIMER_FREQ > 1000
+#error TIMER_FREQ <= 1000 recommended
+#endif
+
+/* Number of timer ticks that a process gets before being
+ preempted. */
+#define TIME_SLICE 1
+/* Number of timer ticks since OS booted. */
static volatile int64_t ticks;
-static void
-irq20_timer (struct intr_frame *args UNUSED)
-{
- ticks++;
- intr_yield_on_return ();
-}
+static intr_handler_func timer_interrupt;
-/* Sets up the 8254 Programmable Interrupt Timer (PIT) to
+/* Sets up the 8254 Programmable Interval Timer (PIT) to
interrupt PIT_FREQ times per second, and registers the
corresponding interrupt. */
void
outb (0x40, count & 0xff);
outb (0x40, count >> 8);
- intr_register (0x20, 0, INTR_OFF, irq20_timer, "8254 Timer");
+ intr_register (0x20, 0, INTR_OFF, timer_interrupt, "8254 Timer");
}
+/* Returns the number of timer ticks since the OS booted. */
int64_t
timer_ticks (void)
{
return t;
}
+/* Returns the number of timer ticks elapsed since THEN, which
+ should be a value once returned by timer_ticks(). */
int64_t
timer_elapsed (int64_t then)
{
return timer_ticks () - then;
}
-/* Suspends execution for approximately DURATION milliseconds. */
+/* Suspends execution for approximately TICKS timer ticks. */
void
-timer_msleep (int64_t ms)
+timer_sleep (int64_t ticks)
{
- int64_t ticks = (int64_t) ms * TIMER_FREQ / 1000;
int64_t start = timer_ticks ();
+ ASSERT (intr_get_level () == INTR_ON);
while (timer_elapsed (start) < ticks)
- continue;
+ thread_yield ();
}
-void
-timer_usleep (int64_t us)
+/* Returns MS milliseconds in timer ticks, rounding up. */
+int64_t
+timer_ms2ticks (int64_t ms)
{
- timer_msleep (us / 1000 + 1);
+ /* MS / 1000 s
+ ------------------------ = MS * TIMER_FREQ / 1000 ticks.
+ (1 / TIMER_FREQ) ticks/s
+ */
+ return DIV_ROUND_UP (ms * TIMER_FREQ, 1000);
}
+/* Returns US microseconds in timer ticks, rounding up. */
+int64_t
+timer_us2ticks (int64_t us)
+{
+ return DIV_ROUND_UP (us * TIMER_FREQ, 1000000);
+}
+
+/* Returns NS nanoseconds in timer ticks, rounding up. */
+int64_t
+timer_ns2ticks (int64_t ns)
+{
+ return DIV_ROUND_UP (ns * TIMER_FREQ, 1000000000);
+}
+
+/* Prints timer statistics. */
void
-timer_nsleep (int64_t ns)
+timer_print_stats (void)
{
- timer_msleep (ns / 1000000 + 1);
+ printf ("Timer: %"PRId64" ticks\n", ticks);
+}
+\f
+/* Timer interrupt handler. */
+static void
+timer_interrupt (struct intr_frame *args UNUSED)
+{
+ ticks++;
+ thread_tick ();
+ if (ticks % TIME_SLICE == 0)
+ intr_yield_on_return ();
}