| 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. |
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| 3 | It is modelled (very losely) after libevent |
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| 4 | (http://monkey.org/~provos/libevent/) and the Event perl module, but aims |
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| 5 | to be faster and more correct, and also more featureful. |
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| 7 | DIFFERENCES AND COMPARISON TO LIBEVENT: |
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| 8 | |
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| 9 | (comparisons relative to libevent-1.3e and libev-0.00, see also the benchmark |
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| 10 | at http://libev.schmorp.de/bench.html). |
2 | (see benchmark at http://libev.schmorp.de/bench.html) |
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| 12 | - multiple watchers can wait for the same event without deregistering others, |
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| 13 | both for file descriptors as well as signals. |
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| 14 | (registering two read events on fd 10 and unregistering one will not |
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| 15 | break the other). |
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| 16 | |
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| 17 | - fork() is supported and can be handled |
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| 18 | (there is no way to recover from a fork when libevent is active). |
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| 19 | |
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| 20 | - timers are handled as a priority queue (important operations are O(1)) |
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| 21 | (libevent uses a much less efficient but more complex red-black tree). |
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| 22 | |
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| 23 | - supports absolute (wallclock-based) timers in addition to relative ones, |
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| 24 | i.e. can schedule timers to occur after n seconds, or at a specific time. |
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| 25 | |
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| 26 | - timers can be repeating (both absolute and relative ones). |
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| 27 | |
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| 28 | - detects time jumps and adjusts timers |
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| 29 | (works for both forward and backward time jumps and also for absolute timers). |
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| 31 | - race-free signal processing |
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| 32 | (libevent may delay processing signals till after the next event). |
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| 33 | |
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| 34 | - less calls to epoll_ctl |
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| 35 | (stopping and starting an io watcher between two loop iterations will now |
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| 36 | result in spuriois epoll_ctl calls). |
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| 37 | |
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| 38 | - usually less calls to gettimeofday and clock_gettime |
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| 39 | (libevent calls it on every timer event change, libev twice per iteration). |
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| 40 | |
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| 41 | - watchers use less memory |
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| 42 | (libevent on amd64: 152 bytes, libev: <= 56 bytes). |
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| 43 | |
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| 44 | - library uses less memory |
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| 45 | (libevent allocates large data structures wether used or not, libev |
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| 46 | scales all its data structures dynamically). |
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| 47 | |
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| 48 | - no hardcoded arbitrary limits |
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| 49 | (libevent contains an off-by-one bug and sometimes hardcodes a limit of |
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| 50 | 32000 fds). |
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| 51 | |
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| 52 | - libev separates timer, signal and io watchers from each other |
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| 53 | (libevent combines them, but with libev you can combine them yourself |
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| 54 | by reusing the same callback and still save memory). |
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| 55 | |
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| 56 | - simpler design, backends are potentially much simpler |
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| 57 | (in libevent, backends have to deal with watchers, thus the problems) |
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| 58 | (epoll backend in libevent: 366 lines, libev: 90 lines, and more features). |
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| 59 | |
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| 60 | - libev handles EBADF gracefully by removing the offending fds. |
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| 61 | |
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| 62 | - doesn't rely on nonportable BSD header files. |
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| 63 | |
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| 64 | - a event.h compatibility header exists, and can be used to run a wide |
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| 65 | range of libevent programs unchanged (such as evdns.c). |
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| 66 | |
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| 67 | - win32 compatibility for the core parts. |
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| 68 | |
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| 69 | - the event core library (ev and event layer) compiles and works both as |
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| 70 | C and C++. |
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| 71 | |
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| 72 | whats missing? |
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| 73 | |
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| 74 | - no event-like priority support at the moment (the ev priorities |
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| 75 | are not yet finished and work differently, but you cna use idle watchers |
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| 76 | to get a similar effect). |
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| 77 | |
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| 78 | |
4 | |
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5 | ABOUT |
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6 | |
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7 | Homepage: http://software.schmorp.de/pkg/libev |
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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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11 | |
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12 | Libev is modelled (very losely) after libevent and the Event perl |
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13 | module, but is faster, scales better and is more correct, and also more |
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14 | featureful. And also smaller. Yay. |
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15 | |
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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 | |
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41 | Examples of programs that embed libev: the EV perl module, auditd, |
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42 | rxvt-unicode, gvpe (GNU Virtual Private Ethernet), the Deliantra MMORPG |
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43 | server (http://www.deliantra.net/), Rubinius (a next-generation Ruby |
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44 | VM), the Ebb web server, the Rev event toolkit. |
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45 | |
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46 | |
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47 | CONTRIBUTORS |
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48 | |
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49 | libev was written and designed by Marc Lehmann and Emanuele Giaquinta. |
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50 | |
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51 | The following people sent in patches or made other noteworthy |
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52 | contributions to the design (for minor patches, see the Changes |
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53 | file. If I forgot to include you, please shout at me, it was an |
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54 | accident): |
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55 | |
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56 | W.C.A. Wijngaards |
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57 | Christopher Layne |
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58 | Chris Brody |
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59 | |
