ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/README
Revision: 1.2
Committed: Tue Oct 30 23:10:33 2007 UTC (17 years ago) by root
Branch: MAIN
Changes since 1.1: +54 -4 lines
Log Message:
much better

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