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16 years ago
libev is a high-performance event loop/event model with lots of features.
It is modelled (very losely) after libevent
( and the Event perl module, but aims
to be faster and more correct, and also more featureful.
(comparisons relative to libevent-1.3e and libev-0.00, see also the benchmark
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- multiple watchers can wait for the same event without deregistering others,
both for file descriptors as well as signals.
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(registering two read events on fd 10 and unregistering one will not
break the other).
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- fork() is supported and can be handled
(there is no way to recover from a fork when libevent is active).
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- timers are handled as a priority queue (important operations are O(1))
(libevent uses a much less efficient but more complex red-black tree).
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- supports absolute (wallclock-based) timers in addition to relative ones,
i.e. can schedule timers to occur after n seconds, or at a specific time.
- timers can be repeating (both absolute and relative ones).
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- detects time jumps and adjusts timers
(works for both forward and backward time jumps and also for absolute timers).
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- race-free signal processing
(libevent may delay processing signals till after the next event).
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- less calls to epoll_ctl
(stopping and starting an io watcher between two loop iterations will now
result in spuriois epoll_ctl calls).
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- usually less calls to gettimeofday and clock_gettime
(libevent calls it on every timer event change, libev twice per iteration).
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- watchers use less memory
(libevent on amd64: 152 bytes, libev: <= 56 bytes).
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- library uses less memory
(libevent allocates large data structures wether used or not, libev
scales all its data structures dynamically).
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- no hardcoded arbitrary limits
(libevent contains an off-by-one bug and sometimes hardcodes a limit of
32000 fds).
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- libev separates timer, signal and io watchers from each other
(libevent combines them, but with libev you can combine them yourself
by reusing the same callback and still save memory).
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- simpler design, backends are potentially much simpler
(in libevent, backends have to deal with watchers, thus the problems)
(epoll backend in libevent: 366 lines, libev: 90 lines, and more features).
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- libev handles EBADF gracefully by removing the offending fds.
- doesn't rely on nonportable BSD header files.
- a event.h compatibility header exists, and can be used to run a wide
range of libevent programs unchanged (such as evdns.c).
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whats missing?
- evbuffer, evhttp, bufferevent are missing.
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- no priority support at the moment (but likely to be delivered later).
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- kqueue, poll (libev currently implements epoll and select).
16 years ago
- windows support (whats windows?).