[kernel][thread] Track per-thread scheduling statistics

Track per-thread runtime, last scheduled time, and count of times
scheduled. Query via existing threadstats CLI.

kernel/debug.c

@@ -87,6 +87,7 @@ static int cmd_threadstats(int argc, const console_cmd_args *argv) {
         printf("\ttimers: %lu\n", thread_stats[i].timers);
     }
 
+    dump_threads_stats();
     return 0;
 }
 

kernel/include/kernel/thread.h

@@ -69,6 +69,14 @@ enum thread_tls_list {
 
 #define THREAD_MAGIC (0x74687264) // 'thrd'
 
+#if THREAD_STATS
+struct thread_specific_stats {
+    lk_bigtime_t total_run_time;
+    lk_bigtime_t last_run_timestamp;
+    ulong schedules; // times this thread is scheduled to run.
+};
+#endif
+
 typedef struct thread {
     int magic;
     struct list_node thread_list_node;
@@ -110,6 +118,10 @@ typedef struct thread {
     uintptr_t tls[MAX_TLS_ENTRY];
 
     char name[32];
+
+#if THREAD_STATS
+    struct thread_specific_stats stats;
+#endif
 } thread_t;
 
 #if WITH_SMP
@@ -163,6 +175,7 @@ void dump_thread(thread_t *t);
 void arch_dump_thread(thread_t *t);
 void dump_all_threads(void);
 void dump_all_threads_unlocked(void);
+void dump_threads_stats(void);
 
 /* scheduler routines */
 void thread_yield(void); /* give up the cpu voluntarily */

kernel/thread.c

@@ -516,12 +516,17 @@ void thread_resched(void) {
 #if THREAD_STATS
     THREAD_STATS_INC(context_switches);
 
+    lk_bigtime_t now = current_time_hires();
     if (thread_is_idle(oldthread)) {
-        lk_bigtime_t now = current_time_hires();
         thread_stats[cpu].idle_time += now - thread_stats[cpu].last_idle_timestamp;
+    } else {
+        oldthread->stats.total_run_time += now - oldthread->stats.last_run_timestamp;
     }
     if (thread_is_idle(newthread)) {
-        thread_stats[cpu].last_idle_timestamp = current_time_hires();
+        thread_stats[cpu].last_idle_timestamp = now;
+    } else {
+        newthread->stats.last_run_timestamp = now;
+        newthread->stats.schedules++;
     }
 #endif
 
@@ -1010,6 +1015,32 @@ void dump_all_threads(void) {
     THREAD_UNLOCK(state);
 }
 
+#if THREAD_STATS
+void dump_threads_stats(void) {
+    thread_t *t;
+
+    THREAD_LOCK(state);
+    list_for_every_entry (&thread_list, t, thread_t, thread_list_node) {
+        if (t->magic != THREAD_MAGIC) {
+            dprintf(INFO, "bad magic on thread struct %p, aborting.\n", t);
+            hexdump(t, sizeof(thread_t));
+            break;
+        }
+        if (thread_is_idle(t)) {
+            continue;
+        }
+        // thread specific stats
+        dprintf(INFO, "\t(%s):\n", t->name);
+        dprintf(INFO, "\t\tScheduled: %ld\n", t->stats.schedules);
+        uint percent = (t->stats.total_run_time * 10000) / current_time_hires();
+        dprintf(INFO, "\t\tTotal run time: %lld, %u.%02u%%\n", t->stats.total_run_time,
+                percent / 100, percent % 100);
+        dprintf(INFO, "\t\tLast time run: %lld\n", t->stats.last_run_timestamp);
+    }
+    THREAD_UNLOCK(state);
+}
+#endif
+
 /** @} */