[mono] Enable startup stats timer on wasm (#41994)

* Set clock in mono_clock_init if available and add wasm definitions

This matches the OSX behavior and cleans things up a bit. We also now call this cross-platform, so don't error when called on Windows

* Add new "real time" counter based on clock_gettime

The initial value is set early in mono_main as part of mono_counters_init. This is needed because /proc/stat does not exist with emscripten and we need a way to measure time on wasm

src/mono/mono/mini/mini-posix.c

@@ -523,6 +523,7 @@ static clock_serv_t sampling_clock;
 static void
 clock_init_for_profiler (MonoProfilerSampleMode mode)
 {
+	mono_clock_init (&sampling_clock);
 }
 
 static void
@@ -691,7 +692,6 @@ sampling_thread_func (gpointer unused)
 		goto init;
 	}
 
-	mono_clock_init (&sampling_clock);
 	clock_init_for_profiler (mode);
 
 	for (guint64 sleep = mono_clock_get_time_ns (sampling_clock); mono_atomic_load_i32 (&sampling_thread_running); clock_sleep_ns_abs (sleep)) {

src/mono/mono/utils/mono-counters.c

@@ -8,9 +8,11 @@
 #include <stdlib.h>
 #include <glib.h>
 #include "config.h"
-#include "mono-counters.h"
-#include "mono-proclib.h"
-#include "mono-os-mutex.h"
+
+#include "mono/utils/mono-counters.h"
+#include "mono/utils/mono-proclib.h"
+#include "mono/utils/mono-os-mutex.h"
+#include "mono/utils/mono-time.h"
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
@@ -27,6 +29,9 @@ struct _MonoCounter {
 static MonoCounter *counters = NULL;
 static mono_mutex_t counters_mutex;
 
+static mono_clock_id_t real_time_clock;
+static guint64 real_time_start;
+
 static volatile gboolean initialized = FALSE;
 
 static int valid_mask = 0;
@@ -131,6 +136,9 @@ mono_counters_init (void)
 
 	mono_os_mutex_init (&counters_mutex);
 
+	mono_clock_init (&real_time_clock);
+	real_time_start = mono_clock_get_time_ns (real_time_clock);
+
 	initialize_system_counters ();
 
 	initialized = TRUE;
@@ -311,6 +319,12 @@ total_time (void)
 	return mono_process_get_data (GINT_TO_POINTER (mono_process_current_pid ()), MONO_PROCESS_TOTAL_TIME);
 }
 
+static guint64
+real_time (void)
+{
+	return mono_clock_get_time_ns (real_time_clock) - real_time_start;
+}
+
 static gint64
 working_set (void)
 {
@@ -411,6 +425,7 @@ initialize_system_counters (void)
 	register_internal ("User Time", SYSCOUNTER_TIME, (gpointer) &user_time, sizeof (gint64));
 	register_internal ("System Time", SYSCOUNTER_TIME, (gpointer) &system_time, sizeof (gint64));
 	register_internal ("Total Time", SYSCOUNTER_TIME, (gpointer) &total_time, sizeof (gint64));
+	register_internal ("Real Time", SYSCOUNTER_TIME, (gpointer) &real_time, sizeof (guint64));
 	register_internal ("Working Set", SYSCOUNTER_BYTES, (gpointer) &working_set, sizeof (gint64));
 	register_internal ("Private Bytes", SYSCOUNTER_BYTES, (gpointer) &private_bytes, sizeof (gint64));
 	register_internal ("Virtual Bytes", SYSCOUNTER_BYTES, (gpointer) &virtual_bytes, sizeof (gint64));

src/mono/mono/utils/mono-time.c

@@ -279,11 +279,16 @@ mono_clock_get_time_ns (mono_clock_id_t clk_id)
 	return ((guint64) mach_ts.tv_sec * 1000000000) + (guint64) mach_ts.tv_nsec;
 }
 
-#elif defined(__linux__)
+// TODO: Potentially make this the default?
+// Can we assume clock_gettime exists on all modern POSIX systems? Maybe add a better check for it in configure.ac?
+#elif defined(__linux__) || defined (TARGET_WASM)
 
 void
 mono_clock_init (mono_clock_id_t *clk_id)
-{	
+{
+#ifdef HAVE_CLOCK_MONOTONIC
+	*clk_id = CLOCK_MONOTONIC;
+#endif
 }
 
 void
@@ -307,22 +312,20 @@ mono_clock_get_time_ns (mono_clock_id_t clk_id)
 void
 mono_clock_init (mono_clock_id_t *clk_id)
 {
-	// TODO: need to implement this function for PC
-	g_assert_not_reached ();
+	// TODO: need to implement this function for Windows
 }
 
 void
 mono_clock_cleanup (mono_clock_id_t clk_id)
 {
-	// TODO: need to implement this function for PC
-	g_assert_not_reached ();
+	// TODO: need to implement this function for Windows
 }
 
 guint64
 mono_clock_get_time_ns (mono_clock_id_t clk_id)
 {
-	// TODO: need to implement time stamp function for PC
-	g_assert_not_reached ();
+	// TODO: need to implement time stamp function for Windows
+	return 0;
 }
 
 #endif