ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.pod
(Generate patch)

Comparing libev/ev.pod (file contents):
Revision 1.365 by root, Mon Jan 31 00:07:21 2011 UTC vs.
Revision 1.368 by root, Thu Apr 14 23:02:33 2011 UTC

… …
483=item C<EVBACKEND_EPOLL> (value 4, Linux) 483=item C<EVBACKEND_EPOLL> (value 4, Linux)
484 484
485Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 485Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
486kernels). 486kernels).
487 487
488For few fds, this backend is a bit little slower than poll and select, 488For few fds, this backend is a bit little slower than poll and select, but
489but it scales phenomenally better. While poll and select usually scale 489it scales phenomenally better. While poll and select usually scale like
490like O(total_fds) where n is the total number of fds (or the highest fd), 490O(total_fds) where total_fds is the total number of fds (or the highest
491epoll scales either O(1) or O(active_fds). 491fd), epoll scales either O(1) or O(active_fds).
492 492
493The epoll mechanism deserves honorable mention as the most misdesigned 493The epoll mechanism deserves honorable mention as the most misdesigned
494of the more advanced event mechanisms: mere annoyances include silently 494of the more advanced event mechanisms: mere annoyances include silently
495dropping file descriptors, requiring a system call per change per file 495dropping file descriptors, requiring a system call per change per file
496descriptor (and unnecessary guessing of parameters), problems with dup, 496descriptor (and unnecessary guessing of parameters), problems with dup,
… …
2151 2151
2152Another way to think about it (for the mathematically inclined) is that 2152Another way to think about it (for the mathematically inclined) is that
2153C<ev_periodic> will try to run the callback in this mode at the next possible 2153C<ev_periodic> will try to run the callback in this mode at the next possible
2154time where C<time = offset (mod interval)>, regardless of any time jumps. 2154time where C<time = offset (mod interval)>, regardless of any time jumps.
2155 2155
2156For numerical stability it is preferable that the C<offset> value is near 2156The C<interval> I<MUST> be positive, and for numerical stability, the
2157C<ev_now ()> (the current time), but there is no range requirement for 2157interval value should be higher than C<1/8192> (which is around 100
2158this value, and in fact is often specified as zero. 2158microseconds) and C<offset> should be higher than C<0> and should have
2159at most a similar magnitude as the current time (say, within a factor of
2160ten). Typical values for offset are, in fact, C<0> or something between
2161C<0> and C<interval>, which is also the recommended range.
2159 2162
2160Note also that there is an upper limit to how often a timer can fire (CPU 2163Note also that there is an upper limit to how often a timer can fire (CPU
2161speed for example), so if C<interval> is very small then timing stability 2164speed for example), so if C<interval> is very small then timing stability
2162will of course deteriorate. Libev itself tries to be exact to be about one 2165will of course deteriorate. Libev itself tries to be exact to be about one
2163millisecond (if the OS supports it and the machine is fast enough). 2166millisecond (if the OS supports it and the machine is fast enough).
… …
4204F<event.h> that are not directly supported by the libev core alone. 4207F<event.h> that are not directly supported by the libev core alone.
4205 4208
4206In standalone mode, libev will still try to automatically deduce the 4209In standalone mode, libev will still try to automatically deduce the
4207configuration, but has to be more conservative. 4210configuration, but has to be more conservative.
4208 4211
4212=item EV_USE_FLOOR
4213
4214If defined to be C<1>, libev will use the C<floor ()> function for its
4215periodic reschedule calculations, otherwise libev will fall back on a
4216portable (slower) implementation. If you enable this, you usually have to
4217link against libm or something equivalent. Enabling this when the C<floor>
4218function is not available will fail, so the safe default is to not enable
4219this.
4220
4209=item EV_USE_MONOTONIC 4221=item EV_USE_MONOTONIC
4210 4222
4211If defined to be C<1>, libev will try to detect the availability of the 4223If defined to be C<1>, libev will try to detect the availability of the
4212monotonic clock option at both compile time and runtime. Otherwise no 4224monotonic clock option at both compile time and runtime. Otherwise no
4213use of the monotonic clock option will be attempted. If you enable this, 4225use of the monotonic clock option will be attempted. If you enable this,
… …
5224The physical time that is observed. It is apparently strictly monotonic :) 5236The physical time that is observed. It is apparently strictly monotonic :)
5225 5237
5226=item wall-clock time 5238=item wall-clock time
5227 5239
5228The time and date as shown on clocks. Unlike real time, it can actually 5240The time and date as shown on clocks. Unlike real time, it can actually
5229be wrong and jump forwards and backwards, e.g. when the you adjust your 5241be wrong and jump forwards and backwards, e.g. when you adjust your
5230clock. 5242clock.
5231 5243
5232=item watcher 5244=item watcher
5233 5245
5234A data structure that describes interest in certain events. Watchers need 5246A data structure that describes interest in certain events. Watchers need

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines