Hi!

On 14/08/25 17:08, Gabriele Monaco wrote:

...

+/*
+ * ha_monitor_init_env - setup timer and reset all environment
+ *
+ * Called from a hook in the DA start functions, it supplies the da_mon
+ * corresponding to the current ha_mon.
+ * Not all hybrid automata require the timer, still set it for simplicity.
+ */
+static inline void ha_monitor_init_env(struct da_monitor *da_mon)
+{
+	struct ha_monitor *ha_mon = to_ha_monitor(da_mon);
+
+	ha_monitor_reset_all_stored(ha_mon);
+	if (unlikely(!ha_mon->timer.base))
+		hrtimer_setup(&ha_mon->timer, ha_monitor_timer_callback,
+			      CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+}

...

+/*
+ * Helper functions to handle the monitor timer.
+ * Not all monitors require a timer, in such case the timer will be set up but
+ * never armed.
+ * Timers start since the last reset of the supplied env or from now if env is
+ * not an environment variable. If env was not initialised no timer starts.
+ * Timers can expire on any CPU unless the monitor is per-cpu,
+ * where we assume every event occurs on the local CPU.
+ */
+static inline void ha_start_timer_ns(struct ha_monitor *ha_mon, enum envs env,
+				     u64 expire)
+{
+	int mode = HRTIMER_MODE_REL;
+	u64 passed = 0;
+
+	if (env >= 0 && env < ENV_MAX_STORED) {
+		if (ha_monitor_env_invalid(ha_mon, env))
+			return;
+		passed = ha_get_env(ha_mon, env);
+	}
+	if (RV_MON_TYPE == RV_MON_PER_CPU)
+		mode |= HRTIMER_MODE_PINNED;
+	hrtimer_start(&ha_mon->timer, ns_to_ktime(expire - passed), mode);
+}

Does this also need to be _HARD on RT for the monitor to work?

Also, my only concern with the usage of per-task timers is that
reprogramming add overhead, so I wonder if this gets noticeable when
running some kind of performance sensitive workload in production (as it
was reported for dl-server). Did you test such a case?

Thanks!
Juri