tests/xtimer_overhead: initial commit

tests/xtimer_overhead/Makefile

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+DEVELHELP ?= 0
+include ../Makefile.tests_common
+
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include

tests/xtimer_overhead/README.md

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+# Introduction
+
+This test application measures 1024 times how much overhead xtimer adds.

tests/xtimer_overhead/main.c

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+/*
+ * Copyright (C) 2020 Kaspar Schleiser <kaspar@schleiser.de>
+ *               2020 Freie Universität Berlin
+ *               2020 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     test
+ * @{
+ *
+ * @file
+ * @brief       xtimer overhead test application
+ *
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * @}
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <inttypes.h>
+
+#include "xtimer.h"
+
+#define BASE    1000
+#define SAMPLES 1024
+
+int32_t xtimer_overhead(uint32_t base);
+
+int main(void)
+{
+    uint32_t total = 0;
+
+    int32_t min = INT32_MAX;
+    int32_t max = INT32_MIN;
+
+    unsigned n = SAMPLES;
+    while (n--) {
+        int32_t overhead = xtimer_overhead(BASE);
+        total += labs(overhead);
+        if (overhead < min) {
+            min = overhead;
+        }
+        else if (overhead > max) {
+            max = overhead;
+        }
+    }
+
+    printf("min=%" PRIi32 " max=%" PRIi32 " avg_diff=%" PRIi32 "\n", min, max,
+           (total / SAMPLES));
+
+    return 0;
+}

tests/xtimer_overhead/overhead.c

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+/*
+ * Copyright (C) 2020 Kaspar Schleiser <kaspar@schleiser.de>
+ *               2020 Freie Universität Berlin
+ *               2020 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @ingroup     sys_xtimer_overhead
+ * @{
+ *
+ * @file
+ * @brief       xtimer overhead measurement functions
+ *
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * @}
+ */
+
+#include "xtimer.h"
+
+typedef struct {
+    volatile uint32_t *val;
+} callback_arg_t;
+
+static void _callback(void *arg)
+{
+    callback_arg_t *callback_arg = (callback_arg_t *)arg;
+
+    *callback_arg->val = xtimer_now_usec();
+}
+
+int32_t xtimer_overhead(uint32_t base)
+{
+    volatile uint32_t after = 0;
+    uint32_t pre;
+
+    callback_arg_t arg = { .val = &after };
+    xtimer_t t = { .callback = _callback, .arg = &arg };
+
+    pre = xtimer_now_usec();
+    xtimer_set(&t, base);
+    while (!after) {}
+    return after - pre - base;
+}

tests/xtimer_overhead/tests/01-run.py

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+#!/usr/bin/env python3
+
+# Copyright (C) 2019 Kaspar Schleiser <kaspar@schleiser.de>
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import sys
+from testrunner import run
+
+
+def testfunc(child):
+    child.expect(r"min=-?\d+ max=-?\d+ avg_diff=\d+\r\n")
+
+
+if __name__ == "__main__":
+    sys.exit(run(testfunc))