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libev is modelled after libevent (, but aims
to be faster and more correct, and also more featureful. Examples:
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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)
- fork() is supported and can be handled
(there is no way to recover from a fork when libevent is active)
- timers are handled as a priority queue
(libevent uses a less efficient red-black tree)
- 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)
- detects time jumps and adjusts timers
(works for both forward and backward time jumps and also for absolute timers)
- can correctly remove timers while executing callbacks
(libevent doesn't handle this reliably and can crash)
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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)
- usually less calls to gettimeofday and clock_gettime
(libevent calls it on every timer event change, libev twice per iteration)
- watchers use less memory
(libevent on amd64: 152 bytes, libev: <= 56 bytes)
- library uses less memory
(libevent allocates large data structures wether used or not, libev
scales all its data structures dynamically)
- no hardcoded arbitrary limits
(libevent contains an off-by-one bug and sometimes hardcodes a limit of
32000 fds)
- 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)
- 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: 89 lines, and more features)
whats missing?
- evdns, evhttp, bufferevent are missing, libev is only an even library at
the moment.
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- no priority support at the moment
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- kqueue, poll (libev currently implements epoll and select)
- windows support (whats windows?)