diff --git a/include/proto/activity.h b/include/proto/activity.h
new file mode 100644
index 0000000..4cf9c8d
--- /dev/null
+++ b/include/proto/activity.h
@@ -0,0 +1,69 @@
+/*
+ * include/proto/activity.h
+ * This file contains macros and inline functions for activity measurements.
+ *
+ * Copyright (C) 2000-2018 Willy Tarreau - w@1wt.eu
+ *
+ * This library 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, version 2.1
+ * exclusively.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef _PROTO_ACTIVITY_H
+#define _PROTO_ACTIVITY_H
+
+#include <common/config.h>
+#include <common/hathreads.h>
+#include <common/time.h>
+#include <types/activity.h>
+
+extern struct activity activity[MAX_THREADS];
+
+
+void report_stolen_time(uint64_t stolen);
+
+/* Collect date and time information before calling poll(). This will be used
+ * to count the run time of the past loop and the sleep time of the next poll.
+ */
+static inline void activity_count_runtime()
+{
+	uint64_t new_mono_time;
+	uint64_t new_cpu_time;
+	int64_t stolen;
+
+	new_cpu_time   = now_cpu_time();
+	new_mono_time  = now_mono_time();
+
+	if (prev_cpu_time && prev_mono_time) {
+		new_cpu_time  -= prev_cpu_time;
+		new_mono_time -= prev_mono_time;
+		stolen = new_mono_time - new_cpu_time;
+		if (unlikely(stolen >= 500000)) {
+			stolen /= 500000;
+			/* more than half a millisecond difference might
+			 * indicate an undesired preemption.
+			 */
+			report_stolen_time(stolen);
+		}
+	}
+}
+
+
+#endif /* _PROTO_ACTIVITY_H */
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */