diff --git a/src/Makefile.am b/src/Makefile.am
index f4b293925bfcfdf989889db768d60e3de778c985..b75bd93c24913c96817afc409e397e808d43b4d9 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -35,13 +35,13 @@ endif
# List required headers
include_HEADERS = space.h runner.h queue.h task.h lock.h cell.h part.h const.h \
engine.h swift.h serial_io.h timers.h debug.h scheduler.h proxy.h parallel_io.h \
- common_io.h single_io.h multipole.h map.h tools.h partition.h
+ common_io.h single_io.h multipole.h map.h tools.h partition.h clocks.h
# Common source files
AM_SOURCES = space.c runner.c queue.c task.c cell.c engine.c \
serial_io.c timers.c debug.c scheduler.c proxy.c parallel_io.c \
units.c common_io.c single_io.c multipole.c version.c map.c \
- kernel.c tools.c part.c partition.c
+ kernel.c tools.c part.c partition.c clocks.c
# Include files for distribution, not installation.
nobase_noinst_HEADERS = approx_math.h atomic.h cycle.h error.h inline.h kernel.h vector.h \
diff --git a/src/clocks.c b/src/clocks.c
new file mode 100644
index 0000000000000000000000000000000000000000..0d0e89bac3ccb05420a5ca21ccb54dbabfa93783
--- /dev/null
+++ b/src/clocks.c
@@ -0,0 +1,145 @@
+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2016 Peter W. Draper (p.w.draper@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+/**
+ * @file clocks.c
+ * @brief support for measuring intervals in seconds. Use cycle.h
+ * or timers.h for relative times.
+ */
+
+/* Config parameters. */
+#include "../config.h"
+
+/* Standard headers. */
+#include <stdio.h>
+#include <unistd.h>
+
+/* Local headers. */
+#include "clocks.h"
+
+/* 0.25 of a second in nanoseconds. */
+#define SLEEPTIME 250000000
+
+/**
+ * @brief Get the current time.
+ *
+ * @param time the current time.
+ */
+void clocks_gettime(struct clockstime *time) {
+
+#ifdef HAVE_CLOCK_GETTIME
+ clock_gettime(CLOCK_REALTIME, &time->time);
+#else
+ time->time = getticks();
+#endif
+}
+
+
+/**
+ * @brief Get difference in milli-seconds between two times.
+ *
+ * @param start the start time.
+ * @param end the end time.
+ *
+ * @return the difference in milli-secinds.
+ */
+double clocks_diff(struct clockstime *start, struct clockstime *end)
+{
+#ifdef HAVE_CLOCK_GETTIME
+ struct timespec temp;
+ if ((end->time.tv_nsec - start->time.tv_nsec) < 0) {
+ temp.tv_sec = end->time.tv_sec - start->time.tv_sec - 1;
+ temp.tv_nsec = 1000000000 + end->time.tv_nsec - start->time.tv_nsec;
+ } else {
+ temp.tv_sec = end->time.tv_sec - start->time.tv_sec;
+ temp.tv_nsec = end->time.tv_nsec - start->time.tv_nsec;
+ }
+ return (double)temp.tv_sec * 1000.0 + (double)temp.tv_nsec * 1.0E-6;
+#else
+ return elapsed(end->time, start-time) / clocks_cpufreq() * 1000;
+#endif
+
+}
+
+/**
+ * @brief Estimate the CPU frequency in Hz.
+ *
+ * The technique is either to read the value from the cpuinfo_max_freq
+ * file, or use a clock timed nanosleep, or use the macro CPU_TPS.
+ *
+ * Only evaulated once.
+ *
+ * @result the CPU frequency.
+ */
+unsigned long long clocks_cpufreq() {
+ static unsigned long long cpufreq = 0;
+
+ /* If already evaluated return that. */
+ if (cpufreq > 0)
+ return cpufreq;
+
+ /* Look for the system value, if available. */
+#ifdef __linux__
+ FILE *file = fopen("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",
+ "r");
+ if (file != NULL) {
+ unsigned long long maxfreq;
+ if (fscanf(file, "%llu", &maxfreq) == 1) {
+ cpufreq = maxfreq;
+ }
+ fclose(file);
+ }
+#endif
+
+#ifdef HAVE_CLOCK_GETTIME
+ /* If not try to time a nanosleep() in ticks. */
+ if (cpufreq == 0) {
+ struct clockstime time1;
+ struct clockstime time2;
+
+ struct timespec sleep;
+ sleep.tv_sec = 0;
+ sleep.tv_nsec = SLEEPTIME;
+
+ clocks_gettime(&time1);
+ ticks tic = getticks();
+
+ /* Could do some calculation, but constant_tsc should protect us. */
+ nanosleep(&sleep, NULL);
+
+ clocks_gettime(&time2);
+ ticks toc = getticks();
+ double realsleep = clocks_diff(&time1, &time2);
+
+ cpufreq = (signed long long) (double)(toc - tic) * 1.0 / realsleep;
+ }
+#endif
+
+ /* Final attempt */
+#ifdef CPU_TPS
+ if (cpufreq == 0)
+ cpufreq = CPU_TPS;
+#endif
+
+ /* If all fails just report ticks in any times. */
+ if (cpufreq == 0)
+ cpufreq = 1;
+
+ return cpufreq;
+}
diff --git a/src/clocks.h b/src/clocks.h
new file mode 100644
index 0000000000000000000000000000000000000000..b97033029e46e1708d334500dcbf63ceaee46415
--- /dev/null
+++ b/src/clocks.h
@@ -0,0 +1,38 @@
+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2016 Peter W. Draper (p.w.draper@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_CLOCKS_H
+#define SWIFT_CLOCKS_H
+
+#include <time.h>
+#include "cycle.h"
+
+/* Struct to record a time for the clocks functions. */
+struct clockstime {
+#ifdef HAVE_CLOCK_GETTIME
+ struct timespec time;
+#else
+ ticks time;
+#endif
+};
+
+void clocks_gettime(struct clockstime *time);
+double clocks_diff(struct clockstime *start, struct clockstime *end);
+unsigned long long clocks_cpufreq();
+
+#endif /* SWIFT_CLOCKS_H */