| 1 | libev is a high-performance event loop/event model with lots of features. |
1 | libev 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) |
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4 | |
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5 | ABOUT |
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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 |
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9 | http://lists.schmorp.de/cgi-bin/mailman/listinfo/libev |
| 6 | Library Documentation: http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod |
10 | Library Documentation: http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod |
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11 | |
| 8 | It is modelled (very losely) after libevent and the Event perl module, |
12 | Libev is modelled (very loosely) after libevent and the Event perl |
| 9 | but aims to be faster and more correct, and also more featureful. And |
13 | module, but is faster, scales better and is more correct, and also more |
| 10 | also smaller. Yay. |
14 | featureful. And also smaller. Yay. |
| 11 | |
15 | |
| 12 | ABOUT THIS DISTRIBUTION |
16 | Some of the specialties of libev not commonly found elsewhere are: |
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17 | |
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18 | - extensive and detailed, readable documentation (not doxygen garbage). |
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19 | - fully supports fork, can detect fork in various ways and automatically |
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20 | re-arms kernel mechanisms that do not support fork. |
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21 | - highly optimised select, poll, linux epoll, linux aio, bsd kqueue |
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22 | and solaris event ports backends. |
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23 | - filesystem object (path) watching (with optional linux inotify support). |
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24 | - wallclock-based times (using absolute time, cron-like). |
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25 | - relative timers/timeouts (handle time jumps). |
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26 | - fast intra-thread communication between multiple |
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27 | event loops (with optional fast linux eventfd backend). |
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28 | - extremely easy to embed (fully documented, no dependencies, |
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29 | autoconf supported but optional). |
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30 | - very small codebase, no bloated library, simple code. |
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31 | - fully extensible by being able to plug into the event loop, |
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32 | integrate other event loops, integrate other event loop users. |
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33 | - very little memory use (small watchers, small event loop data). |
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34 | - optional C++ interface allowing method and function callbacks |
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35 | at no extra memory or runtime overhead. |
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36 | - optional Perl interface with similar characteristics (capable |
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37 | of running Glib/Gtk2 on libev). |
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38 | - support for other languages (multiple C++ interfaces, D, Ruby, |
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39 | Python) available from third-parties. |
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40 | |
| 14 | If you downloaded the libevent+libev distribution of libev, you will |
41 | Examples of programs that embed libev: the EV perl module, auditd, |
| 15 | find it looks very much like libevent. In fact, the distributed libev |
42 | rxvt-unicode, gvpe (GNU Virtual Private Ethernet), the Deliantra MMORPG |
| 16 | tarballs are indeed libevent tarballs patched up with the libev |
43 | server (http://www.deliantra.net/), Rubinius (a next-generation Ruby |
| 17 | event core, taking the evbuffer, evtag, evdns and evhttpd parts from |
44 | VM), the Ebb web server, the Rev event toolkit. |
| 18 | libevent (they use the libevent emulation inside libev). Configure and |
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| 19 | Makefile stuff is also a more or less direct copy of libevent, and are |
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| 20 | maintained by the libevent authors. |
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45 | |
| 22 | If you downloaded the libev distribution (without libevent), then |
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| 23 | you only get the core parts of the library, meaning http and dns |
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| 24 | client/server code and similar things are missing. Only the core event |
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| 25 | loop is included. |
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| 26 | |
46 | |
| 27 | If you are looking for an easily embeddable version, I recommend using |
47 | CONTRIBUTORS |
| 28 | the libev standalone distribution or the CVS repository. |
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| 29 | |
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| 30 | Examples of programs that embed libev: the EV perl module, |
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| 31 | rxvt-unicode, gvpe (GNU Virtual Private Ethernet) and deliantra |
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| 32 | (http://www.deliantra.net). |
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| 33 | |
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| 34 | DIFFERENCES AND COMPARISON TO LIBEVENT |
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| 35 | |
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| 36 | The comparisons below are relative to libevent-1.3e. |
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| 37 | |
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| 38 | - multiple watchers can wait for the same event without deregistering others, |
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| 39 | both for file descriptors as well as signals. |
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| 40 | (registering two read events on fd 10 and unregistering one will not |
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| 41 | break the other). |
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| 42 | |
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| 43 | - fork() is supported and can be handled |
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| 44 | (there is no way to recover from a fork with libevent). |
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| 45 | |
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| 46 | - timers are handled as a priority queue (important operations are O(1)) |
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| 47 | (libevent uses a much less efficient but more complex red-black tree). |
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| 48 | |
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| 49 | - supports absolute (wallclock-based) timers in addition to relative ones, |
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| 50 | i.e. can schedule timers to occur after n seconds, or at a specific time. |
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| 51 | |
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| 52 | - timers can be repeating (both absolute and relative ones). |
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| 53 | |
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| 54 | - absolute timers can have customised rescheduling hooks (suitable for cron-like |
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| 55 | applications). |
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| 56 | |
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| 57 | - detects time jumps and adjusts timers |
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| 58 | (works for both forward and backward time jumps and also for absolute timers). |
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| 59 | |
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| 60 | - race-free signal processing |
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| 61 | (libevent may delay processing signals till after the next event). |
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| 62 | |
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| 63 | - more efficient epoll backend |
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| 64 | (stopping and starting an io watcher between two loop iterations will not |
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| 65 | result in spurious epoll_ctl calls). |
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| 66 | |
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| 67 | - usually less calls to gettimeofday and clock_gettime |
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| 68 | (libevent calls it on every timer event change, libev twice per iteration). |
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| 69 | |
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| 70 | - watchers use less memory |
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| 71 | (libevent watcher on amd64: 152 bytes, libev native: <= 56 bytes, libevent emulation: 144 bytes). |
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| 73 | - library uses less memory |
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| 74 | (libevent allocates large data structures wether used or not, libev |
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| 75 | scales all its data structures dynamically). |
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| 76 | |
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| 77 | - no hardcoded arbitrary limits |
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| 78 | (libevent contains an off-by-one bug and sometimes hardcodes limits). |
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| 79 | |
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| 80 | - libev separates timer, signal and io watchers from each other |
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| 81 | (libevent combines them, but with libev you can combine them yourself |
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| 82 | by reusing the same callback and still save memory). |
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| 83 | |
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| 84 | - simpler design, backends are potentially much simpler |
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| 85 | (in libevent, backends have to deal with watchers, thus the problems with |
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| 86 | wildly different semantics between diferent backends) |
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| 87 | (epoll backend in libevent: 366 lines no caching, libev: 90 lines full caching). |
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| 88 | |
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| 89 | - libev handles EBADF gracefully by removing the offending fds. |
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| 90 | |
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| 91 | - libev communicates errors to the callback, libevent to the |
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| 92 | event adder or not at all. |
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| 93 | |
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| 94 | - doesn't rely on nonportable BSD header files. |
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| 95 | |
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| 96 | - an event.h compatibility header exists, and can be used to run a wide |
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| 97 | range of libevent programs unchanged (such as evdns.c). |
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| 98 | |
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| 99 | - win32 compatibility for the core parts. |
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| 100 | (the backend is fd-based as documented and on other platforms, |
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| 101 | not handle-based like libevent, and can be used for both winscoket environments |
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| 102 | and unix-like ones). |
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| 103 | |
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| 104 | - libev can be embedded easily with or without autoconf support into |
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| 105 | other programs, with no changes to the source code necessary. |
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| 106 | |
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| 107 | - the event core library (ev and event layer) compiles and works both as |
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| 108 | C and C++. |
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| 109 | |
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| 110 | - a simple C++ wrapper that supports methods as callbacks exists. |
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| 111 | |
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| 112 | - a full featured and widely used perl module is available. |
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| 113 | |
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| 114 | whats missing? |
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| 115 | |
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| 116 | - no event-like priority support at the moment (the ev priorities work |
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| 117 | differently, but you can use idle watchers to get a similar effect). |
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| 118 | |
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| 119 | AUTHOR |
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| 120 | |
48 | |
| 121 | libev was written and designed by Marc Lehmann and Emanuele Giaquinta. |
49 | libev was written and designed by Marc Lehmann and Emanuele Giaquinta. |
| 122 | |
50 | |
| 123 | The following people sent in patches or made other noteworthy |
51 | The following people sent in patches or made other noteworthy |
| 124 | contributions to the design (if I forgot to include you, please shout |
52 | contributions to the design (for minor patches, see the Changes |
| 125 | at me, it was an accident): |
53 | file. If I forgot to include you, please shout at me, it was an |
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54 | accident): |
| 126 | |
55 | |
| 127 | W.C.A. Wijngaards |
56 | W.C.A. Wijngaards |
| 128 | Christopher Layne |
57 | Christopher Layne |
| 129 | Chris Brody |
58 | Chris Brody |
| 130 | |
59 | |
