On Mon, Oct 23, 2006 at 11:04:49AM -0700, Edward Chan wrote: > HI there, > > I just started taking a look at libevent and had a couple questions. > > 1. are the event_* api's thread safe?
So far as you can guarantee there is no contention for the struct event and struct event_base objects. > 2. how do you use EV_PERSIST flag? I'm used to using poll where I add > interest for read or write, then when the socket is readable/writable, I > remove my interest for that event until my read/write would block again, > then I add back my interest for this event again. You can continue doing it this way, without using the EV_PERSIST flag. But there are two other methods: 1) If that particular event is the core driver of all other events, you simply set EV_PERSIST and let it drive everything else. E.g. the way evbuffers are implemented. 2) You invert your typical poll methodology. Use EV_PERSIST and then use event_del() when you do NOT want any more notifications. In many scenarios, when a descriptor isn't blocking you continue reading/writing until it _does_ block, w/ the expectation that your application can run faster than the socket buffers can be re-filled. This is a sort of a middle ground between the method you originally described and the higher-order #1 method. Note that with poll and select you don't lose much by shifting an event in and out of a polling state. However, with things like epoll() and kqueue() you potentially incur a system call everytime you do switch the notification state of each descriptor, which is costly. _______________________________________________ Libevent-users mailing list Libevent-users@monkey.org http://monkey.org/mailman/listinfo/libevent-users
