| 1 | libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims |
1 | libev is a high-performance event loop/event model with lots of features. |
| 2 | to be faster and more correct, and also more featureful. Examples: |
2 | (see benchmark at http://libev.schmorp.de/bench.html) |
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3 | |
| 4 | - multiple watchers can wait for the same event without deregistering others. |
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| 5 | (registering two read events on fd 10 and unregistering one will not |
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| 6 | break the other) |
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| 8 | - fork() is supported and can be handled |
5 | ABOUT |
| 9 | (there is no way to recover from a fork when libevent is active) |
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6 | |
| 11 | - timers are handled as a priority queue |
7 | Homepage: http://software.schmorp.de/pkg/libev |
| 12 | (libevent uses a less efficient red-black tree) |
8 | Mailinglist: libev@lists.schmorp.de |
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9 | http://lists.schmorp.de/cgi-bin/mailman/listinfo/libev |
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10 | Library Documentation: http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod |
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| 14 | - supports absolute (wallclock-based) timers in addition to relative ones, |
12 | Libev is modelled (very losely) after libevent and the Event perl |
| 15 | i.e. can schedule timers to occur after n seconds, or at a specific time. |
13 | module, but is faster, scales better and is more correct, and also more |
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14 | featureful. And also smaller. Yay. |
| 16 | |
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| 17 | - timers can be repeating (both absolute and relative ones) |
16 | Some of the specialties of libev not commonly found elsewhere are: |
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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, epoll, kqueue and event ports backends. |
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22 | - filesystem object (path) watching (with optional linux inotify support). |
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23 | - wallclock-based times (using absolute time, cron-like). |
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24 | - relative timers/timeouts (handle time jumps). |
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25 | - fast intra-thread communication between multiple |
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26 | event loops (with optional fast linux eventfd backend). |
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27 | - extremely easy to embed. |
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28 | - very small codebase, no bloated library. |
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29 | - fully extensible by being able to plug into the event loop, |
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30 | integrate other event loops, integrate other event loop users. |
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31 | - very little memory use (small watchers, small event loop data). |
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32 | - optional C++ interface allowing method and function callbacks |
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33 | at no extra memory or runtime overhead. |
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34 | - optional Perl interface with similar characteristics (capable |
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35 | of running Glib/Gtk2 on libev, interfaces with Net::SNMP and |
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36 | libadns). |
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37 | - support for other languages (multiple C++ interfaces, D, Ruby, |
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38 | Python) available from third-parties. |
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39 | |
| 19 | - detects time jumps and adjusts timers |
40 | Examples of programs that embed libev: the EV perl module, |
| 20 | (works for both forward and backward time jumps and also for absolute timers) |
41 | rxvt-unicode, gvpe (GNU Virtual Private Ethernet), the Deliantra MMORPG |
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42 | server (http://www.deliantra.net/), Rubinius (a next-generation Ruby |
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43 | VM), the Ebb web server, the Rev event toolkit. |
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44 | |
| 22 | - can correctly remove timers while executing callbacks |
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| 23 | (libevent doesn't handle this reliably and can crash) |
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45 | |
| 25 | - race-free signal processing |
46 | CONTRIBUTORS |
| 26 | (libevent may delay processing signals till after the next event) |
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47 | |
| 28 | - less calls to epoll_ctl |
48 | libev was written and designed by Marc Lehmann and Emanuele Giaquinta. |
| 29 | (stopping and starting an io watcher between two loop iterations will now |
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| 30 | result in spuriois epoll_ctl calls) |
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| 31 | |
49 | |
| 32 | - usually less calls to gettimeofday and clock_gettime |
50 | The following people sent in patches or made other noteworthy |
| 33 | (libevent calls it on every timer event change, libev twice per iteration) |
51 | contributions to the design (for minor patches, see the Changes |
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52 | file. If I forgot to include you, please shout at me, it was an |
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53 | accident): |
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54 | |
| 35 | - watchers use less memory |
55 | W.C.A. Wijngaards |
| 36 | (libevent on amd64: 152 bytes, libev: <= 56 bytes) |
56 | Christopher Layne |
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57 | Chris Brody |
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58 | |
| 38 | - library uses less memory |
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| 39 | (libevent allocates large data structures wether used or not, libev |
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| 40 | scales all its data structures dynamically) |
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| 41 | |
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| 42 | - no hardcoded arbitrary limits |
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| 43 | (libevent contains an off-by-one bug and sometimes hardcodes a limit of |
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| 44 | 32000 fds) |
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| 45 | |
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| 46 | - libev separates timer, signal and io watchers from each other |
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| 47 | (libevent combines them, but with libev you can combine them yourself |
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| 48 | by reusing the same callback and still save memory) |
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| 49 | |
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| 50 | - simpler design, backends are potentially much simpler |
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| 51 | (in libevent, backends have to deal with watchers, thus the problems) |
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| 52 | (epoll backend in libevent: 366 lines, libev: 89 lines, and more features) |
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| 53 | |
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| 54 | whats missing? |
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| 55 | |
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| 56 | - evdns, evhttp, bufferevent are missing, libev is only an even library at |
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| 57 | the moment. |
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| 58 | |
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| 59 | - no priority support at the moment. |
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| 61 | - kqueue, poll (libev currently implements epoll and select). |
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