| 1 | libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims |
1 | libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims |
| 2 | to be faster and more correct, and also more featureful. Examples: |
2 | to be faster and more correct, and also more featureful. Examples: |
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3 | |
| 4 | - multiple watchers can wait for the same event without deregistering others. |
4 | - multiple watchers can wait for the same event without deregistering others, |
| 5 | - fork() is supported and can be handled. |
5 | both for file descriptors as well as signals. |
| 6 | - timers are handled as a priority queue (faster) |
6 | (registering two read events on fd 10 and unregistering one will not |
| 7 | - watchers use less memory (faster) |
7 | break the other) |
| 8 | - less calls to epoll_ctl (faster) |
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9 | - fork() is supported and can be handled |
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10 | (there is no way to recover from a fork when libevent is active) |
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11 | |
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12 | - timers are handled as a priority queue |
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13 | (libevent uses a less efficient red-black tree) |
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15 | - supports absolute (wallclock-based) timers in addition to relative ones, |
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16 | i.e. can schedule timers to occur after n seconds, or at a specific time. |
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17 | |
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18 | - timers can be repeating (both absolute and relative ones) |
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19 | |
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20 | - detects time jumps and adjusts timers |
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21 | (works for both forward and backward time jumps and also for absolute timers) |
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22 | |
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23 | - can correctly remove timers while executing callbacks |
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24 | (libevent doesn't handle this reliably and can crash) |
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25 | |
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26 | - race-free signal processing |
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27 | (libevent may delay processing signals till after the next event) |
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28 | |
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29 | - less calls to epoll_ctl |
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30 | (stopping and starting an io watcher between two loop iterations will now |
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31 | result in spuriois epoll_ctl calls) |
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32 | |
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33 | - usually less calls to gettimeofday and clock_gettime |
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34 | (libevent calls it on every timer event change, libev twice per iteration) |
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35 | |
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36 | - watchers use less memory |
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37 | (libevent on amd64: 152 bytes, libev: <= 56 bytes) |
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38 | |
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39 | - library uses less memory |
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40 | (libevent allocates large data structures wether used or not, libev |
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41 | scales all its data structures dynamically) |
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42 | |
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43 | - no hardcoded arbitrary limits |
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44 | (libevent contains an off-by-one bug and sometimes hardcodes a limit of |
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45 | 32000 fds) |
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46 | |
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47 | - libev separates timer, signal and io watchers from each other |
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48 | (libevent combines them, but with libev you can combine them yourself |
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49 | by reusing the same callback and still save memory) |
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50 | |
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51 | - simpler design, backends are potentially much simpler |
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52 | (in libevent, backends have to deal with watchers, thus the problems) |
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53 | (epoll backend in libevent: 366 lines, libev: 89 lines, and more features) |
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54 | |
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55 | whats missing? |
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56 | |
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57 | - evdns, evhttp, bufferevent are missing, libev is only an even library at |
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58 | the moment. |
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59 | |
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60 | - no priority support at the moment |
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61 | |
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62 | - kqueue, poll (libev currently implements epoll and select) |
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63 | |
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64 | - windows support (whats windows?) |
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65 | |
