Addition rtdsc for tracing purposes

server/include/rdtsc.h

@@ -0,0 +1,61 @@
+#ifndef _RDTSC_H
+#define _RDTSC_H
+/*
+ * This file is distributed as part of the SkySQL Gateway.  It is free
+ * software: you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation,
+ * version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Copyright SkySQL Ab 2014
+ */
+
+/**
+ * @file rdtsc.h Access the process time-stamp counter
+ *
+ * This is an Intel only facilty that is used to access an accurate time
+ * value, the granularity of which is related to the processor clock speed
+ * and the overhead for access is much lower than using any system call
+ * mechanism.
+ *
+ *
+ * @verbatim
+ * Revision History
+ *
+ * Date		Who		Description
+ * 19/09/2014	Mark Riddoch	Initial implementation
+ *
+ * @endverbatim
+ */
+
+typedef unsigned long long CYCLES;
+
+/**
+ * Get the current time-stamp counter value from the processor. This is the
+ * count of CPU cyceles as a 64 bit value.
+ *
+ * The value returned is related to the clock speed, to obtian a value in
+ * seconds divide the returned value by the clock frequency for the processor.
+ *
+ * Note, on multi-processsor systems care much be taken to avoid the thread
+ * moving to a different processor when taken succsive value of RDTSC to
+ * obtian accurate timing. This may be done by setting pocessor affinity for
+ * the thread. See sched_setaffinity/sched_getaffinity.
+ *
+ * @return CPU cycle count
+ */
+static __inline__ CYCLES rdtsc(void)
+{
+    unsigned long long int x;
+    __asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
+    return x;
+}
+#endif