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Revision: 1.6
Committed: Wed Oct 31 18:28:00 2007 UTC (16 years, 6 months ago) by root
Branch: MAIN
Changes since 1.5: +2 -0 lines
Log Message:
add prepare watcher

File Contents

# Content
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:
3
4 (comparisons relative to libevent-1.3e and libev-0.00)
5
6 - multiple watchers can wait for the same event without deregistering others,
7 both for file descriptors as well as signals.
8 (registering two read events on fd 10 and unregistering one will not
9 break the other)
10
11 - fork() is supported and can be handled
12 (there is no way to recover from a fork when libevent is active)
13
14 - timers are handled as a priority queue
15 (libevent uses a less efficient red-black tree)
16
17 - supports absolute (wallclock-based) timers in addition to relative ones,
18 i.e. can schedule timers to occur after n seconds, or at a specific time.
19
20 - timers can be repeating (both absolute and relative ones)
21
22 - detects time jumps and adjusts timers
23 (works for both forward and backward time jumps and also for absolute timers)
24
25 - can correctly remove timers while executing callbacks
26 (libevent doesn't handle this reliably and can crash)
27
28 - race-free signal processing
29 (libevent may delay processing signals till after the next event)
30
31 - less calls to epoll_ctl
32 (stopping and starting an io watcher between two loop iterations will now
33 result in spuriois epoll_ctl calls)
34
35 - usually less calls to gettimeofday and clock_gettime
36 (libevent calls it on every timer event change, libev twice per iteration)
37
38 - watchers use less memory
39 (libevent on amd64: 152 bytes, libev: <= 56 bytes)
40
41 - library uses less memory
42 (libevent allocates large data structures wether used or not, libev
43 scales all its data structures dynamically)
44
45 - no hardcoded arbitrary limits
46 (libevent contains an off-by-one bug and sometimes hardcodes a limit of
47 32000 fds)
48
49 - libev separates timer, signal and io watchers from each other
50 (libevent combines them, but with libev you can combine them yourself
51 by reusing the same callback and still save memory)
52
53 - simpler design, backends are potentially much simpler
54 (in libevent, backends have to deal with watchers, thus the problems)
55 (epoll backend in libevent: 366 lines, libev: 90 lines, and more features)
56
57 - libev handles EBADF gracefully by removing the offending fds.
58
59 whats missing?
60
61 - evdns, evhttp, bufferevent are missing, libev is only an even library at
62 the moment.
63
64 - no priority support at the moment
65
66 - kqueue, poll (libev currently implements epoll and select)
67
68 - windows support (whats windows?)
69