+ if (!queue_empty(&queue->head))
+ deadline = CE(call)->deadline;
+ else
+ deadline = UINT64_MAX;
+
+ timer_call_unlock(queue);
+
+ return (deadline);
+}
+
+
+extern int serverperfmode;
+uint32_t timer_queue_migrate_lock_skips;
+/*
+ * timer_queue_migrate() is called by etimer_queue_migrate()
+ * to move timer requests from the local processor (queue_from)
+ * to a target processor's (queue_to).
+ */
+int
+timer_queue_migrate(mpqueue_head_t *queue_from, mpqueue_head_t *queue_to)
+{
+ timer_call_t call;
+ timer_call_t head_to;
+ int timers_migrated = 0;
+
+ DBG("timer_queue_migrate(%p,%p)\n", queue_from, queue_to);
+
+ assert(!ml_get_interrupts_enabled());
+ assert(queue_from != queue_to);
+
+ if (serverperfmode) {
+ /*
+ * if we're running a high end server
+ * avoid migrations... they add latency
+ * and don't save us power under typical
+ * server workloads
+ */
+ return -4;
+ }
+
+ /*
+ * Take both local (from) and target (to) timer queue locks while
+ * moving the timers from the local queue to the target processor.
+ * We assume that the target is always the boot processor.
+ * But only move if all of the following is true:
+ * - the target queue is non-empty
+ * - the local queue is non-empty
+ * - the local queue's first deadline is later than the target's
+ * - the local queue contains no non-migrateable "local" call
+ * so that we need not have the target resync.
+ */
+
+ timer_call_lock_spin(queue_to);
+
+ head_to = TIMER_CALL(queue_first(&queue_to->head));
+ if (queue_empty(&queue_to->head)) {
+ timers_migrated = -1;
+ goto abort1;
+ }
+
+ timer_call_lock_spin(queue_from);
+
+ if (queue_empty(&queue_from->head)) {
+ timers_migrated = -2;
+ goto abort2;
+ }
+
+ call = TIMER_CALL(queue_first(&queue_from->head));
+ if (CE(call)->deadline < CE(head_to)->deadline) {
+ timers_migrated = 0;
+ goto abort2;
+ }
+
+ /* perform scan for non-migratable timers */
+ do {
+ if (call->flags & TIMER_CALL_LOCAL) {
+ timers_migrated = -3;
+ goto abort2;
+ }
+ call = TIMER_CALL(queue_next(qe(call)));
+ } while (!queue_end(&queue_from->head, qe(call)));
+
+ /* migration loop itself -- both queues are locked */
+ while (!queue_empty(&queue_from->head)) {
+ call = TIMER_CALL(queue_first(&queue_from->head));
+ if (!simple_lock_try(&call->lock)) {
+ /* case (2b) lock order inversion, dequeue only */
+ timer_queue_migrate_lock_skips++;
+ (void) remque(qe(call));
+ call->async_dequeue = TRUE;
+ continue;
+ }
+ timer_call_entry_dequeue(call);
+ timer_call_entry_enqueue_deadline(
+ call, queue_to, CE(call)->deadline);
+ timers_migrated++;
+ simple_unlock(&call->lock);
projects / apple / xnu.git / blobdiff