libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims to be faster and more correct, and also more featureful. Examples: - multiple watchers can wait for the same event without deregistering others. (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) - 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. - no priority support at the moment. - kqueue, poll (libev currently implements epoll and select).