Messages in this thread | | | Date | Mon, 27 Dec 2004 23:05:09 +0300 | From | Paul P Komkoff Jr <> | Subject | How to implement multithreaded event loop ? |
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Hi!
I am trying to implement a multithreaded event loop using epoll. So, I have 2 kind of events. First, there are conditions on fds I have (listener sockets, client connections, my connections to other clients). Second, I need to have some kind of priority queue into which I can push forthcoming timed events.
In case of single-threaded server, this is fairly trivial. I just need to make heap queue and add its 1st (i.e. minimal) element as timeout to each next epoll_wait call. When some condition breaks the wait, I can always do find_min and wait again with new timeout.
Things become complicated when I need to scale. So, without this timeout cruft, I can just add proper locking around my data structures but main epoll_wait loop is multithread-aware, e.g. it will retrieve different events for different waiting threads (to be absolutely fair with you, I did not implemented this part yet, but I assume that some combination of edge triggered + one shot epoll will do the trick). But, if using heap priority queue to manage timed events, I need to wake up each waiting thread when any event was added to the heap before one that was minimal.
From all I've read about it, waking up all waiting thread isn't trivial.
Another solution proposed by my poor brain is - to have alive thread which will handle this priority queue, and have one fifo fd in my epoll set dedicated to this purpose. Priority queue management thread will write single char to that fd when some timed event needs to be processed.
Doing some google search, I've found this message: http://www.uwsg.iu.edu/hypermail/linux/kernel/0210.3/2416.html Things can be much easier if there was timer kernel object (or its equivalent). Can anyone give me some advice - how I should solve this problem?
Thanks in advance.
-- Paul P 'Stingray' Komkoff Jr // http://stingr.net/key <- my pgp key This message represents the official view of the voices in my head - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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