| 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: |
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| 4 | - multiple watchers can wait for the same event without deregistering others. |
3 | It is modelled (very losely) after libevent |
| 5 | - fork() is supported and can be handled. |
4 | (http://monkey.org/~provos/libevent/) and the Event perl module, but aims |
| 6 | - timers are handled as a priority queue (faster) |
5 | to be faster and more correct, and also more featureful. |
| 7 | - watchers use less memory (faster) |
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| 8 | - less calls to epoll_ctl (faster) |
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7 | DIFFERENCES AND COMPARISON TO LIBEVENT: |
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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). |
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11 | |
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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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30 | |
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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 | - evbuffer, evhttp, bufferevent are missing. |
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75 | |
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76 | - no priority support at the moment (but likely to be delivered later). |
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77 | |
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78 | - kqueue, poll (libev currently implements epoll and select). |
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79 | |
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80 | - windows support (whats windows?). |
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81 | |
