Everywhere: Improve CPU usage calculation

As threads come and go, we can't simply account for how many time
slices the threads at any given point may have been using. We need to
also account for threads that have since disappeared. This means we
also need to track how many time slices we have expired globally.

However, because this doesn't account for context switches outside of
the system timer tick values may still be under-reported. To solve this
we will need to track more accurate time information on each context
switch.

This also fixes top's cpu usage calculation which was still based on
the number of context switches.

Fixes #6473

1 files changed, 6 insertions, 0 deletions

diff --git a/Kernel/Scheduler.h b/Kernel/Scheduler.h
index c703df83a6..3cabdaa9b7 100644
--- a/Kernel/Scheduler.h
+++ b/Kernel/Scheduler.h
@@ -24,6 +24,11 @@ extern WaitQueue* g_finalizer_wait_queue;
 extern Atomic<bool> g_finalizer_has_work;
 extern RecursiveSpinLock g_scheduler_lock;
 
+struct TotalTicksScheduled {
+    u64 total { 0 };
+    u64 total_kernel { 0 };
+};
+
 class Scheduler {
 public:
     static void initialize();
@@ -49,6 +54,7 @@ public:
     static void queue_runnable_thread(Thread&);
     static void dump_scheduler_state(bool = false);
     static bool is_initialized();
+    static TotalTicksScheduled get_total_ticks_scheduled();
 };
 
 }