-libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims
-to be faster and more correct, and also more featureful. Examples:
+libev is a high-performance event loop/event model with lots of features.
-- multiple watchers can wait for the same event without deregistering others.
+It is modelled (very losely) after libevent
+(http://monkey.org/~provos/libevent/) and the Event perl module, but aims
+to be faster and more correct, and also more featureful.
+
+DIFFERENCES AND COMPARISON TO LIBEVENT:
+
+(comparisons relative to libevent-1.3e and libev-0.00, see also the benchmark
+at http://libev.schmorp.de/bench.html).
+
+- multiple watchers can wait for the same event without deregistering others,
+ both for file descriptors as well as signals.
(registering two read events on fd 10 and unregistering one will not
- break the other)
+ break the other).
- fork() is supported and can be handled
- (there is no way to recover from a fork when libevent is active)
+ (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)
+- timers are handled as a priority queue (important operations are O(1))
+ (libevent uses a much less efficient but more complex 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)
+- 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)
+ (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)
+- race-free signal processing
+ (libevent may delay processing signals till after the next event).
- less calls to epoll_ctl
(stopping and starting an io watcher between two loop iterations will now
- result in spuriois epoll_ctl calls)
+ 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)
+ (libevent calls it on every timer event change, libev twice per iteration).
- watchers use less memory
- (libevent on amd64: 152 bytes, libev: <= 56 bytes)
+ (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)
+ 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)
+ 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)
+ 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)
+ (epoll backend in libevent: 366 lines, libev: 90 lines, and more features).
-whats missing?
+- libev handles EBADF gracefully by removing the offending fds.
+
+- doesn't rely on nonportable BSD header files.
-- evdns, evhttp, bufferevent are missing, libev is only an even library at
- the moment.
+- a event.h compatibility header exists, and can be used to run a wide
+ range of libevent programs unchanged (such as evdns.c).
+
+- win32 compatibility for the core parts.
+
+- the event core library (ev and event layer) compiles and works both as
+ C and C++.
+
+whats missing?
-- no priority support at the moment.
+- no event-like priority support at the moment (the ev priorities
+ are not yet finished and work differently, but you can use idle watchers
+ to get a similar effect).
-- kqueue, poll (libev currently implements epoll and select).
projects / software / libev.git / blobdiff