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| -rw-r--r-- | ev.pod | 19 |
1 files changed, 13 insertions, 6 deletions
@@ -1199,18 +1199,25 @@ year, it will still time out after (roughly) and hour. "Roughly" because detecting time jumps is hard, and some inaccuracies are unavoidable (the monotonic clock option helps a lot here). +The callback is guaranteed to be invoked only after its timeout has passed, +but if multiple timers become ready during the same loop iteration then +order of execution is undefined. + +=head3 The special problem of time updates + +Requesting the current time is a costly operation (it usually takes at +least two syscalls): EV therefore updates it's idea of the current time +only before and after C<ev_loop> polls for new events, which causes the +difference between C<ev_now ()> and C<ev_time ()>. + The relative timeouts are calculated relative to the C<ev_now ()> time. This is usually the right thing as this timestamp refers to the time of the event triggering whatever timeout you are modifying/starting. If -you suspect event processing to be delayed and you I<need> to base the timeout -on the current time, use something like this to adjust for this: +you suspect event processing to be delayed and you I<need> to base the +timeout on the current time, use something like this to adjust for this: ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); -The callback is guaranteed to be invoked only after its timeout has passed, -but if multiple timers become ready during the same loop iteration then -order of execution is undefined. - =head3 Watcher-Specific Functions and Data Members =over 4 |