Index: uspace/lib/c/include/perf.h
===================================================================
--- uspace/lib/c/include/perf.h	(revision 7e85d2be0102c8f5b4a85409e870435ac1c03f11)
+++ uspace/lib/c/include/perf.h	(revision 7e85d2be0102c8f5b4a85409e870435ac1c03f11)
@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2018 Vojtech Horky
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * - The name of the author may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/** @addtogroup libc
+ * @{
+ */
+/** @file
+ * System performance measurement utilities.
+ */
+
+#ifndef LIBC_PERF_H_
+#define LIBC_PERF_H_
+
+#include <time.h>
+
+/** Stopwatch is THE way to measure elapsed time on HelenOS. */
+typedef struct {
+	struct timespec start;
+	struct timespec end;
+} stopwatch_t;
+
+#define STOPWATCH_INITIALIZE_STATIC { { 0, 0 }, { 0, 0 } }
+
+/** Initialize system stopwatch.
+ *
+ * @param stopwatch Stopwatch to initialize.
+ */
+static inline void stopwatch_init(stopwatch_t *stopwatch)
+{
+	stopwatch->start.tv_sec = 0;
+	stopwatch->start.tv_nsec = 0;
+	stopwatch->end.tv_sec = 0;
+	stopwatch->end.tv_nsec = 0;
+}
+
+/** Emulate elapsed time for use in tests.
+ *
+ * @param stopwatch Stopwatch to use.
+ * @param nanos Elapsed time in nanoseconds to set.
+ */
+static inline void stopwatch_set_elapsed(stopwatch_t *stopwatch, nsec_t nanos)
+{
+	stopwatch->start.tv_sec = 0;
+	stopwatch->start.tv_nsec = 0;
+	stopwatch->end.tv_sec = NSEC2SEC(nanos);
+	stopwatch->end.tv_nsec = nanos - SEC2NSEC(stopwatch->end.tv_sec);
+}
+
+/** Start the stopwatch.
+ *
+ * @param stopwatch Stopwatch to start.
+ */
+static inline void stopwatch_start(stopwatch_t *stopwatch)
+{
+	getuptime(&stopwatch->start);
+}
+
+/** Stop the stopwatch.
+ *
+ * @param stopwatch Stopwatch to stop.
+ */
+static inline void stopwatch_stop(stopwatch_t *stopwatch)
+{
+	getuptime(&stopwatch->end);
+}
+
+/** Get elapsed time in nanoseconds.
+ *
+ * @param stopwatch Stopwatch to read from.
+ * @return Elapsed time in nanoseconds.
+ */
+static inline nsec_t stopwatch_get_nanos(stopwatch_t *stopwatch)
+{
+	return ts_sub_diff(&stopwatch->end, &stopwatch->start);
+}
+
+#endif
+
+/** @}
+ */