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Revision 1.18 by root, Wed Nov 21 05:05:40 2007 UTC vs.
Revision 1.21 by root, Fri Mar 30 17:43:55 2012 UTC

1libev is a high-performance event loop/event model with lots of features. 1libev is a high-performance event loop/event model with lots of features.
2(see benchmark at http://libev.schmorp.de/bench.html) 2(see benchmark at http://libev.schmorp.de/bench.html)
3 3
4
5ABOUT
6
4 Homepage: http://software.schmorp.de/pkg/libev 7 Homepage: http://software.schmorp.de/pkg/libev
5 E-Mail: libev@lists.schmorp.de 8 Mailinglist: libev@lists.schmorp.de
9 http://lists.schmorp.de/cgi-bin/mailman/listinfo/libev
10 Library Documentation: http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod
6 11
7 It is modelled (very losely) after libevent 12 Libev is modelled (very losely) after libevent and the Event perl
8 (http://monkey.org/~provos/libevent/) and the Event perl module, but aims 13 module, but is faster, scales better and is more correct, and also more
9 to be faster and more correct, and also more featureful. 14 featureful. And also smaller. Yay.
10 15
11ABOUT THIS DISTRIBUTION 16 Some of the specialties of libev not commonly found elsewhere are:
17
18 - extensive and detailed, readable documentation (not doxygen garbage).
19 - fully supports fork, can detect fork in various ways and automatically
20 re-arms kernel mechanisms that do not support fork.
21 - highly optimised select, poll, epoll, kqueue and event ports backends.
22 - filesystem object (path) watching (with optional linux inotify support).
23 - wallclock-based times (using absolute time, cron-like).
24 - relative timers/timeouts (handle time jumps).
25 - fast intra-thread communication between multiple
26 event loops (with optional fast linux eventfd backend).
27 - extremely easy to embed (fully documented, no dependencies,
28 autoconf supported but optional).
29 - very small codebase, no bloated library, simple code.
30 - fully extensible by being able to plug into the event loop,
31 integrate other event loops, integrate other event loop users.
32 - very little memory use (small watchers, small event loop data).
33 - optional C++ interface allowing method and function callbacks
34 at no extra memory or runtime overhead.
35 - optional Perl interface with similar characteristics (capable
36 of running Glib/Gtk2 on libev).
37 - support for other languages (multiple C++ interfaces, D, Ruby,
38 Python) available from third-parties.
12 39
13 If you downloaded a distribution of libev, you will find it looks 40 Examples of programs that embed libev: the EV perl module, node.js,
14 very much like libevent. In fact, the distributed libev tarballs are 41 auditd, rxvt-unicode, gvpe (GNU Virtual Private Ethernet), the
15 indeed libevent tarballs patched up with the libev event core, taking 42 Deliantra MMORPG server (http://www.deliantra.net/), Rubinius (a
16 the evbuffer, evtag, evdns and evhttpd parts from libevent (they use 43 next-generation Ruby VM), the Ebb web server, the Rev event toolkit.
17 the libevent emulation inside libev). Configure and Makefile stuff is
18 also a more or less direct copy of libevent, and are maintained by the
19 libevent authors.
20 44
21 If you are looking for an easily embeddable version, I recommend using
22 the CVS repository (linked from the homepage, above), which contains
23 only the libev core parts.
24 45
25 Examples of programs that embed libev: the EV perl module, 46CONTRIBUTORS
26 rxvt-unicode, gvpe (GNU Virtual Private Ethernet) and deliantra
27 (http://www.deliantra.net).
28
29DIFFERENCES AND COMPARISON TO LIBEVENT
30
31 The comparisons below are relative to libevent-1.3e.
32
33 - multiple watchers can wait for the same event without deregistering others,
34 both for file descriptors as well as signals.
35 (registering two read events on fd 10 and unregistering one will not
36 break the other).
37
38 - fork() is supported and can be handled
39 (there is no way to recover from a fork with libevent).
40
41 - timers are handled as a priority queue (important operations are O(1))
42 (libevent uses a much less efficient but more complex red-black tree).
43
44 - supports absolute (wallclock-based) timers in addition to relative ones,
45 i.e. can schedule timers to occur after n seconds, or at a specific time.
46
47 - timers can be repeating (both absolute and relative ones).
48
49 - absolute timers can have customised rescheduling hooks (suitable for cron-like
50 applications).
51
52 - detects time jumps and adjusts timers
53 (works for both forward and backward time jumps and also for absolute timers).
54
55 - race-free signal processing
56 (libevent may delay processing signals till after the next event).
57
58 - more efficient epoll backend
59 (stopping and starting an io watcher between two loop iterations will not
60 result in spurious epoll_ctl calls).
61
62 - usually less calls to gettimeofday and clock_gettime
63 (libevent calls it on every timer event change, libev twice per iteration).
64
65 - watchers use less memory
66 (libevent watcher on amd64: 152 bytes, libev native: <= 56 bytes, libevent emulation: 144 bytes).
67
68 - library uses less memory
69 (libevent allocates large data structures wether used or not, libev
70 scales all its data structures dynamically).
71
72 - no hardcoded arbitrary limits
73 (libevent contains an off-by-one bug and sometimes hardcodes limits).
74
75 - libev separates timer, signal and io watchers from each other
76 (libevent combines them, but with libev you can combine them yourself
77 by reusing the same callback and still save memory).
78
79 - simpler design, backends are potentially much simpler
80 (in libevent, backends have to deal with watchers, thus the problems with
81 wildly different semantics between diferent backends)
82 (epoll backend in libevent: 366 lines no caching, libev: 90 lines full caching).
83
84 - libev handles EBADF gracefully by removing the offending fds.
85
86 - libev communicates errors to the callback, libevent to the
87 event adder or not at all.
88
89 - doesn't rely on nonportable BSD header files.
90
91 - an event.h compatibility header exists, and can be used to run a wide
92 range of libevent programs unchanged (such as evdns.c).
93
94 - win32 compatibility for the core parts.
95 (the backend is fd-based as documented and on other platforms,
96 not handle-based like libevent, and can be used for both winscoket environments
97 and unix-like ones).
98
99 - libev can be embedded easily with or without autoconf support into
100 other programs, with no changes to the source code necessary.
101
102 - the event core library (ev and event layer) compiles and works both as
103 C and C++.
104
105 - a simple C++ wrapper that supports methods as callbacks exists.
106
107 - a full featured and widely used perl module is available.
108
109 whats missing?
110
111 - no event-like priority support at the moment (the ev priorities work
112 differently, but you can use idle watchers to get a similar effect).
113
114AUTHOR
115 47
116 libev was written and designed by Marc Lehmann and Emanuele Giaquinta. 48 libev was written and designed by Marc Lehmann and Emanuele Giaquinta.
117 49
118 The following people sent in patches or made other noteworthy 50 The following people sent in patches or made other noteworthy
119 contributions to the design (if I forgot to include you, please shout 51 contributions to the design (for minor patches, see the Changes
120 at me, it was an accident): 52 file. If I forgot to include you, please shout at me, it was an
53 accident):
121 54
122 W.C.A. Wijngaards 55 W.C.A. Wijngaards
123 Christopher Layne 56 Christopher Layne
124 Chris Brody 57 Chris Brody
125 58

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