added --enable-rdtsc configure option to enhance timer performance, especially in virtualized environments; default disabled - credits to sirius_black

git-svn-id: https://svn.code.sf.net/p/rathena/svn/trunk@14265 54d463be-8e91-2dee-dedb-b68131a5f0ec

configure.in

@@ -74,6 +74,30 @@ AC_ARG_ENABLE(
 	[enable_debug="no"]
 )
 
+#
+# RDTSC as Tick Source 
+#
+AC_ARG_ENABLE(
+	[rdtsc],
+	AC_HELP_STRING(
+		[--enable-rdtsc],
+		[
+			Uses rdtsc as timing source (disabled by default)
+			Enable it when you've timing issues.
+
+			(For example:  in conjunction with XEN or Other Virtualization mechanisms)
+		
+			Note:
+				Please ensure that you've disabled dynamic CPU-Frequencys, such as power saving options.
+				(On the most modern Dedicated Servers cpufreq is preconfigured, see your distribution's manual
+				 how to disable it)
+		]
+	),
+	[
+		enable_rdtsc=1
+	],
+	[enable_rdtsc=0]
+)
 
 #
 # Profiler
@@ -383,6 +407,19 @@ case $enable_debug in
 esac
 
 
+#
+# RDTSC
+#
+case $enable_rdtsc in
+	0)
+		#default value
+		;;
+	1)
+		CFLAGS="$CFLAGS -DENABLE_RDTSC"
+		;;
+esac
+
+
 #
 # Profiler
 #

src/common/timer.c

@@ -100,11 +100,52 @@ char* search_timer_func_list(TimerFunc func)
  * 	Get tick time
  *----------------------------*/
 
+#if defined(ENABLE_RDTSC)
+static uint64 RDTSC_BEGINTICK = 0,   RDTSC_CLOCK = 0;
+
+static __inline uint64 _rdtsc(){
+	register union{
+		uint64	qw;
+		uint32 	dw[2];
+	} t;
+
+	asm volatile("rdtsc":"=a"(t.dw[0]), "=d"(t.dw[1]) );
+	
+	return t.qw;
+}
+
+static void rdtsc_calibrate(){
+	uint64 t1, t2;
+	int32 i;
+	
+	ShowStatus("Calibrating Timer Source, please wait... ");
+	
+	RDTSC_CLOCK = 0;
+	
+	for(i = 0; i < 5; i++){
+		t1 = _rdtsc();
+		usleep(1000000); //1000 MS
+		t2 = _rdtsc();
+		RDTSC_CLOCK += (t2 - t1) / 1000; 
+	}
+	RDTSC_CLOCK /= 5;
+	
+	RDTSC_BEGINTICK = _rdtsc();	
+	
+	ShowMessage(" done. (Frequency: %u Mhz)\n", (uint32)(RDTSC_CLOCK/1000) );
+}
+
+#endif
+
 /// platform-abstracted tick retrieval
 static unsigned int tick(void)
 {
 #if defined(WIN32)
 	return GetTickCount();
+#elif defined(ENABLE_RDTSC)
+	//
+		return (unsigned int)((_rdtsc() - RDTSC_BEGINTICK) / RDTSC_CLOCK);
+	//
 #elif (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0 && defined(_POSIX_MONOTONIC_CLOCK) /* posix compliant */) || (defined(__FreeBSD_cc_version) && __FreeBSD_cc_version >= 500005 /* FreeBSD >= 5.1.0 */)
 	struct timespec tval;
 	clock_gettime(CLOCK_MONOTONIC, &tval);
@@ -368,6 +409,10 @@ unsigned long get_uptime(void)
 
 void timer_init(void)
 {
+#if defined(ENABLE_RDTSC)
+	rdtsc_calibrate();
+#endif
+
 	time(&start_time);
 }