Kernel: Improve time keeping and dramatically reduce interrupt load

This implements a number of changes related to time:
* If a HPET is present, it is now used only as a system timer, unless
  the Local APIC timer is used (in which case the HPET timer will not
  trigger any interrupts at all).
* If a HPET is present, the current time can now be as accurate as the
  chip can be, independently from the system timer. We now query the
  HPET main counter for the current time in CPU #0's system timer
  interrupt, and use that as a base line. If a high precision time is
  queried, that base line is used in combination with quering the HPET
  timer directly, which should give a much more accurate time stamp at
  the expense of more overhead. For faster time stamps, the more coarse
  value based on the last interrupt will be returned. This also means
  that any missed interrupts should not cause the time to drift.
* The default system interrupt rate is reduced to about 250 per second.
* Fix calculation of Thread CPU usage by using the amount of ticks they
  used rather than the number of times a context switch happened.
* Implement CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE and use it
  for most cases where precise timestamps are not needed.

Libraries/LibC/time.h

@@ -72,6 +72,9 @@ typedef int clockid_t;
 
 #define CLOCK_REALTIME 0
 #define CLOCK_MONOTONIC 1
+#define CLOCK_MONOTONIC_RAW 4
+#define CLOCK_REALTIME_COARSE 5
+#define CLOCK_MONOTONIC_COARSE 6
 #define TIMER_ABSTIME 99
 
 int clock_gettime(clockid_t, struct timespec*);

Libraries/LibC/unistd.cpp

@@ -339,7 +339,7 @@ char* getwd(char* buf)
 int sleep(unsigned seconds)
 {
     struct timespec ts = { seconds, 0 };
-    if (clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, nullptr) < 0)
+    if (clock_nanosleep(CLOCK_MONOTONIC_COARSE, 0, &ts, nullptr) < 0)
         return ts.tv_sec;
     return 0;
 }
@@ -347,7 +347,7 @@ int sleep(unsigned seconds)
 int usleep(useconds_t usec)
 {
     struct timespec ts = { (long)(usec / 1000000), (long)(usec % 1000000) * 1000 };
-    return clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, nullptr);
+    return clock_nanosleep(CLOCK_MONOTONIC_COARSE, 0, &ts, nullptr);
 }
 
 int gethostname(char* buffer, size_t size)

Libraries/LibCore/ElapsedTimer.cpp

@@ -36,7 +36,7 @@ void ElapsedTimer::start()
 {
     m_valid = true;
     timespec now_spec;
-    clock_gettime(CLOCK_MONOTONIC, &now_spec);
+    clock_gettime(m_precise ? CLOCK_MONOTONIC : CLOCK_MONOTONIC_COARSE, &now_spec);
     m_origin_time.tv_sec = now_spec.tv_sec;
     m_origin_time.tv_usec = now_spec.tv_nsec / 1000;
 }
@@ -46,7 +46,7 @@ int ElapsedTimer::elapsed() const
     ASSERT(is_valid());
     struct timeval now;
     timespec now_spec;
-    clock_gettime(CLOCK_MONOTONIC, &now_spec);
+    clock_gettime(m_precise ? CLOCK_MONOTONIC : CLOCK_MONOTONIC_COARSE, &now_spec);
     now.tv_sec = now_spec.tv_sec;
     now.tv_usec = now_spec.tv_nsec / 1000;
     struct timeval diff;

Libraries/LibCore/ElapsedTimer.h

@@ -32,7 +32,10 @@ namespace Core {
 
 class ElapsedTimer {
 public:
-    ElapsedTimer() { }
+    ElapsedTimer(bool precise = false)
+        : m_precise(precise)
+    {
+    }
 
     bool is_valid() const { return m_valid; }
     void start();
@@ -41,6 +44,7 @@ public:
     const struct timeval& origin_time() const { return m_origin_time; }
 
 private:
+    bool m_precise { false };
     bool m_valid { false };
     struct timeval m_origin_time {
         0, 0

Libraries/LibCore/EventLoop.cpp

@@ -580,7 +580,7 @@ retry:
         auto next_timer_expiration = get_next_timer_expiration();
         if (next_timer_expiration.has_value()) {
             timespec now_spec;
-            clock_gettime(CLOCK_MONOTONIC, &now_spec);
+            clock_gettime(CLOCK_MONOTONIC_COARSE, &now_spec);
             now.tv_sec = now_spec.tv_sec;
             now.tv_usec = now_spec.tv_nsec / 1000;
             timeval_sub(next_timer_expiration.value(), now, timeout);
@@ -631,7 +631,7 @@ try_select_again:
 
     if (!s_timers->is_empty()) {
         timespec now_spec;
-        clock_gettime(CLOCK_MONOTONIC, &now_spec);
+        clock_gettime(CLOCK_MONOTONIC_COARSE, &now_spec);
         now.tv_sec = now_spec.tv_sec;
         now.tv_usec = now_spec.tv_nsec / 1000;
     }
@@ -709,7 +709,7 @@ int EventLoop::register_timer(Object& object, int milliseconds, bool should_relo
     timer->interval = milliseconds;
     timeval now;
     timespec now_spec;
-    clock_gettime(CLOCK_MONOTONIC, &now_spec);
+    clock_gettime(CLOCK_MONOTONIC_COARSE, &now_spec);
     now.tv_sec = now_spec.tv_sec;
     now.tv_usec = now_spec.tv_nsec / 1000;
     timer->reload(now);

Libraries/LibCore/ProcessStatisticsReader.cpp

@@ -85,7 +85,8 @@ HashMap<pid_t, Core::ProcessStatistics> ProcessStatisticsReader::get_all()
             thread.times_scheduled = thread_object.get("times_scheduled").to_u32();
             thread.name = thread_object.get("name").to_string();
             thread.state = thread_object.get("state").to_string();
-            thread.ticks = thread_object.get("ticks").to_u32();
+            thread.ticks_user = thread_object.get("ticks_user").to_u32();
+            thread.ticks_kernel = thread_object.get("ticks_kernel").to_u32();
             thread.cpu = thread_object.get("cpu").to_u32();
             thread.priority = thread_object.get("priority").to_u32();
             thread.effective_priority = thread_object.get("effective_priority").to_u32();

Libraries/LibCore/ProcessStatisticsReader.h

@@ -35,7 +35,8 @@ namespace Core {
 struct ThreadStatistics {
     pid_t tid;
     unsigned times_scheduled;
-    unsigned ticks;
+    unsigned ticks_user;
+    unsigned ticks_kernel;
     unsigned syscall_count;
     unsigned inode_faults;
     unsigned zero_faults;

Libraries/LibPthread/pthread.cpp

@@ -474,7 +474,7 @@ int pthread_cond_init(pthread_cond_t* cond, const pthread_condattr_t* attr)
 {
     cond->value = 0;
     cond->previous = 0;
-    cond->clockid = attr ? attr->clockid : CLOCK_MONOTONIC;
+    cond->clockid = attr ? attr->clockid : CLOCK_MONOTONIC_COARSE;
     return 0;
 }
 
@@ -502,7 +502,7 @@ int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex)
 
 int pthread_condattr_init(pthread_condattr_t* attr)
 {
-    attr->clockid = CLOCK_MONOTONIC;
+    attr->clockid = CLOCK_MONOTONIC_COARSE;
     return 0;
 }
 

Libraries/LibPthread/pthread.h

@@ -82,9 +82,9 @@ int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param
     {                                  \
         0, 0, 0, PTHREAD_MUTEX_DEFAULT \
     }
-#define PTHREAD_COND_INITIALIZER \
-    {                            \
-        0, 0, CLOCK_MONOTONIC    \
+#define PTHREAD_COND_INITIALIZER     \
+    {                                \
+        0, 0, CLOCK_MONOTONIC_COARSE \
     }
 
 int pthread_key_create(pthread_key_t* key, void (*destructor)(void*));