Added a PAUSE instruction to the SPIN loop

according to recommendation from Intel.

configure.in

@@ -2342,6 +2342,17 @@ fi
 fi
 #---END:
 
+#Check for x86 PAUSE instruction
+AC_MSG_CHECKING("for x86 PAUSE instruction")
+AC_TRY_COMPILE(
+[],
+[{__asm__ __volatile__ ("pause");}],
+x86_pause_exists=yes, x86_pause_exists=no)
+if test "$x86_pause_exists" = "yes"
+then
+  AC_DEFINE([HAVE_PAUSE_INSTRUCTION], [1], [Does x86 PAUSE instruction exist])
+fi
+
 # Check if pthread_attr_setscope() exists
 AC_CACHE_CHECK("for pthread_attr_setscope", mysql_cv_pthread_attr_setscope,
 AC_TRY_LINK(

storage/innobase/include/ut0ut.h

@@ -17,6 +17,19 @@ Created 1/20/1994 Heikki Tuuri
 
 typedef time_t	ib_time_t;
 
+#ifdef HAVE_PAUSE_INSTRUCTION
+#define PAUSE_INSTRUCTION(volatile_var) {__asm__ __volatile__ ("pause");}
+#elif
+#ifdef UNIV_SYNC_ATOMIC
+#define PAUSE_INSTRUCTION(volatile_var) \
+  { \
+    os_compare_and_swap(volatile_var, 0, 1); \
+  }
+#elif
+#define PAUSE_INSTRUCTION(volatile_var)
+#endif
+#endif
+
 /************************************************************
 Gets the high 32 bits in a ulint. That is makes a shift >> 32,
 but since there seem to be compiler bugs in both gcc and Visual C++,

storage/innobase/ut/ut0ut.c

@@ -336,11 +336,13 @@ ut_delay(
 	ulint	delay)	/* in: delay in microseconds on 100 MHz Pentium */
 {
 	ulint	i, j;
+        volatile lint volatile_var;
 
 	j = 0;
 
 	for (i = 0; i < delay * 50; i++) {
 		j += i;
+                PAUSE_INSTRUCTION(&volatile_var);
 	}
 
 	if (ut_always_false) {