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

Comparing libev/ev.pod (file contents):
Revision 1.244 by root, Mon Jun 29 04:41:34 2009 UTC vs.
Revision 1.247 by root, Wed Jul 8 02:46:05 2009 UTC

… …
620happily wraps around with enough iterations. 620happily wraps around with enough iterations.
621 621
622This value can sometimes be useful as a generation counter of sorts (it 622This value can sometimes be useful as a generation counter of sorts (it
623"ticks" the number of loop iterations), as it roughly corresponds with 623"ticks" the number of loop iterations), as it roughly corresponds with
624C<ev_prepare> and C<ev_check> calls. 624C<ev_prepare> and C<ev_check> calls.
625
626=item unsigned int ev_loop_depth (loop)
627
628Returns the number of times C<ev_loop> was entered minus the number of
629times C<ev_loop> was exited, in other words, the recursion depth.
630
631Outside C<ev_loop>, this number is zero. In a callback, this number is
632C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
633in which case it is higher.
634
635Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
636etc.), doesn't count as exit.
625 637
626=item unsigned int ev_backend (loop) 638=item unsigned int ev_backend (loop)
627 639
628Returns one of the C<EVBACKEND_*> flags indicating the event backend in 640Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629use. 641use.
… …
811 823
812By setting a higher I<io collect interval> you allow libev to spend more 824By setting a higher I<io collect interval> you allow libev to spend more
813time collecting I/O events, so you can handle more events per iteration, 825time collecting I/O events, so you can handle more events per iteration,
814at the cost of increasing latency. Timeouts (both C<ev_periodic> and 826at the cost of increasing latency. Timeouts (both C<ev_periodic> and
815C<ev_timer>) will be not affected. Setting this to a non-null value will 827C<ev_timer>) will be not affected. Setting this to a non-null value will
816introduce an additional C<ev_sleep ()> call into most loop iterations. 828introduce an additional C<ev_sleep ()> call into most loop iterations. The
829sleep time ensures that libev will not poll for I/O events more often then
830once per this interval, on average.
817 831
818Likewise, by setting a higher I<timeout collect interval> you allow libev 832Likewise, by setting a higher I<timeout collect interval> you allow libev
819to spend more time collecting timeouts, at the expense of increased 833to spend more time collecting timeouts, at the expense of increased
820latency/jitter/inexactness (the watcher callback will be called 834latency/jitter/inexactness (the watcher callback will be called
821later). C<ev_io> watchers will not be affected. Setting this to a non-null 835later). C<ev_io> watchers will not be affected. Setting this to a non-null
… …
823 837
824Many (busy) programs can usually benefit by setting the I/O collect 838Many (busy) programs can usually benefit by setting the I/O collect
825interval to a value near C<0.1> or so, which is often enough for 839interval to a value near C<0.1> or so, which is often enough for
826interactive servers (of course not for games), likewise for timeouts. It 840interactive servers (of course not for games), likewise for timeouts. It
827usually doesn't make much sense to set it to a lower value than C<0.01>, 841usually doesn't make much sense to set it to a lower value than C<0.01>,
828as this approaches the timing granularity of most systems. 842as this approaches the timing granularity of most systems. Note that if
843you do transactions with the outside world and you can't increase the
844parallelity, then this setting will limit your transaction rate (if you
845need to poll once per transaction and the I/O collect interval is 0.01,
846then you can't do more than 100 transations per second).
829 847
830Setting the I<timeout collect interval> can improve the opportunity for 848Setting the I<timeout collect interval> can improve the opportunity for
831saving power, as the program will "bundle" timer callback invocations that 849saving power, as the program will "bundle" timer callback invocations that
832are "near" in time together, by delaying some, thus reducing the number of 850are "near" in time together, by delaying some, thus reducing the number of
833times the process sleeps and wakes up again. Another useful technique to 851times the process sleeps and wakes up again. Another useful technique to
834reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure 852reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
835they fire on, say, one-second boundaries only. 853they fire on, say, one-second boundaries only.
854
855Example: we only need 0.1s timeout granularity, and we wish not to poll
856more often than 100 times per second:
857
858 ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859 ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
836 860
837=item ev_loop_verify (loop) 861=item ev_loop_verify (loop)
838 862
839This function only does something when C<EV_VERIFY> support has been 863This function only does something when C<EV_VERIFY> support has been
840compiled in, which is the default for non-minimal builds. It tries to go 864compiled in, which is the default for non-minimal builds. It tries to go
… …
4065=item C<double> must hold a time value in seconds with enough accuracy 4089=item C<double> must hold a time value in seconds with enough accuracy
4066 4090
4067The type C<double> is used to represent timestamps. It is required to 4091The type C<double> is used to represent timestamps. It is required to
4068have at least 51 bits of mantissa (and 9 bits of exponent), which is good 4092have at least 51 bits of mantissa (and 9 bits of exponent), which is good
4069enough for at least into the year 4000. This requirement is fulfilled by 4093enough for at least into the year 4000. This requirement is fulfilled by
4070implementations implementing IEEE 754 (basically all existing ones). 4094implementations implementing IEEE 754, which is basically all existing
4095ones. With IEEE 754 doubles, you get microsecond accuracy until at least
40962200.
4071 4097
4072=back 4098=back
4073 4099
4074If you know of other additional requirements drop me a note. 4100If you know of other additional requirements drop me a note.
4075 4101

Diff Legend

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