… | |
… | |
604 | |
604 | |
605 | Here are the gory details of what C<ev_loop> does: |
605 | Here are the gory details of what C<ev_loop> does: |
606 | |
606 | |
607 | - Before the first iteration, call any pending watchers. |
607 | - Before the first iteration, call any pending watchers. |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
609 | - If a fork was detected, queue and call all fork watchers. |
609 | - If a fork was detected (by any means), queue and call all fork watchers. |
610 | - Queue and call all prepare watchers. |
610 | - Queue and call all prepare watchers. |
611 | - If we have been forked, recreate the kernel state. |
611 | - If we have been forked, detach and recreate the kernel state |
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612 | as to not disturb the other process. |
612 | - Update the kernel state with all outstanding changes. |
613 | - Update the kernel state with all outstanding changes. |
613 | - Update the "event loop time". |
614 | - Update the "event loop time" (ev_now ()). |
614 | - Calculate for how long to sleep or block, if at all |
615 | - Calculate for how long to sleep or block, if at all |
615 | (active idle watchers, EVLOOP_NONBLOCK or not having |
616 | (active idle watchers, EVLOOP_NONBLOCK or not having |
616 | any active watchers at all will result in not sleeping). |
617 | any active watchers at all will result in not sleeping). |
617 | - Sleep if the I/O and timer collect interval say so. |
618 | - Sleep if the I/O and timer collect interval say so. |
618 | - Block the process, waiting for any events. |
619 | - Block the process, waiting for any events. |
619 | - Queue all outstanding I/O (fd) events. |
620 | - Queue all outstanding I/O (fd) events. |
620 | - Update the "event loop time" and do time jump handling. |
621 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
621 | - Queue all outstanding timers. |
622 | - Queue all outstanding timers. |
622 | - Queue all outstanding periodics. |
623 | - Queue all outstanding periodics. |
623 | - If no events are pending now, queue all idle watchers. |
624 | - Unless any events are pending now, queue all idle watchers. |
624 | - Queue all check watchers. |
625 | - Queue all check watchers. |
625 | - Call all queued watchers in reverse order (i.e. check watchers first). |
626 | - Call all queued watchers in reverse order (i.e. check watchers first). |
626 | Signals and child watchers are implemented as I/O watchers, and will |
627 | Signals and child watchers are implemented as I/O watchers, and will |
627 | be handled here by queueing them when their watcher gets executed. |
628 | be handled here by queueing them when their watcher gets executed. |
628 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
629 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
… | |
… | |
633 | anymore. |
634 | anymore. |
634 | |
635 | |
635 | ... queue jobs here, make sure they register event watchers as long |
636 | ... queue jobs here, make sure they register event watchers as long |
636 | ... as they still have work to do (even an idle watcher will do..) |
637 | ... as they still have work to do (even an idle watcher will do..) |
637 | ev_loop (my_loop, 0); |
638 | ev_loop (my_loop, 0); |
638 | ... jobs done. yeah! |
639 | ... jobs done or somebody called unloop. yeah! |
639 | |
640 | |
640 | =item ev_unloop (loop, how) |
641 | =item ev_unloop (loop, how) |
641 | |
642 | |
642 | Can be used to make a call to C<ev_loop> return early (but only after it |
643 | Can be used to make a call to C<ev_loop> return early (but only after it |
643 | has processed all outstanding events). The C<how> argument must be either |
644 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
679 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
680 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
680 | |
681 | |
681 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
682 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
682 | |
683 | |
683 | These advanced functions influence the time that libev will spend waiting |
684 | These advanced functions influence the time that libev will spend waiting |
684 | for events. Both are by default C<0>, meaning that libev will try to |
685 | for events. Both time intervals are by default C<0>, meaning that libev |
685 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
686 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
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687 | latency. |
686 | |
688 | |
687 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
689 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
688 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
690 | allows libev to delay invocation of I/O and timer/periodic callbacks |
689 | increase efficiency of loop iterations. |
691 | to increase efficiency of loop iterations (or to increase power-saving |
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|
692 | opportunities). |
690 | |
693 | |
691 | The background is that sometimes your program runs just fast enough to |
694 | The background is that sometimes your program runs just fast enough to |
692 | handle one (or very few) event(s) per loop iteration. While this makes |
695 | handle one (or very few) event(s) per loop iteration. While this makes |
693 | the program responsive, it also wastes a lot of CPU time to poll for new |
696 | the program responsive, it also wastes a lot of CPU time to poll for new |
694 | events, especially with backends like C<select ()> which have a high |
697 | events, especially with backends like C<select ()> which have a high |
… | |
… | |
709 | Many (busy) programs can usually benefit by setting the I/O collect |
712 | Many (busy) programs can usually benefit by setting the I/O collect |
710 | interval to a value near C<0.1> or so, which is often enough for |
713 | interval to a value near C<0.1> or so, which is often enough for |
711 | interactive servers (of course not for games), likewise for timeouts. It |
714 | interactive servers (of course not for games), likewise for timeouts. It |
712 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
715 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
713 | as this approaches the timing granularity of most systems. |
716 | as this approaches the timing granularity of most systems. |
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717 | |
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|
718 | Setting the I<timeout collect interval> can improve the opportunity for |
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|
719 | saving power, as the program will "bundle" timer callback invocations that |
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720 | are "near" in time together, by delaying some, thus reducing the number of |
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|
721 | times the process sleeps and wakes up again. Another useful technique to |
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|
722 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
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|
723 | they fire on, say, one-second boundaries only. |
714 | |
724 | |
715 | =item ev_loop_verify (loop) |
725 | =item ev_loop_verify (loop) |
716 | |
726 | |
717 | This function only does something when C<EV_VERIFY> support has been |
727 | This function only does something when C<EV_VERIFY> support has been |
718 | compiled in. It tries to go through all internal structures and checks |
728 | compiled in. It tries to go through all internal structures and checks |
… | |
… | |
1662 | will be no polling. |
1672 | will be no polling. |
1663 | |
1673 | |
1664 | =head3 ABI Issues (Largefile Support) |
1674 | =head3 ABI Issues (Largefile Support) |
1665 | |
1675 | |
1666 | Libev by default (unless the user overrides this) uses the default |
1676 | Libev by default (unless the user overrides this) uses the default |
1667 | compilation environment, which means that on systems with optionally |
1677 | compilation environment, which means that on systems with large file |
1668 | disabled large file support, you get the 32 bit version of the stat |
1678 | support disabled by default, you get the 32 bit version of the stat |
1669 | structure. When using the library from programs that change the ABI to |
1679 | structure. When using the library from programs that change the ABI to |
1670 | use 64 bit file offsets the programs will fail. In that case you have to |
1680 | use 64 bit file offsets the programs will fail. In that case you have to |
1671 | compile libev with the same flags to get binary compatibility. This is |
1681 | compile libev with the same flags to get binary compatibility. This is |
1672 | obviously the case with any flags that change the ABI, but the problem is |
1682 | obviously the case with any flags that change the ABI, but the problem is |
1673 | most noticeably with ev_stat and large file support. |
1683 | most noticeably disabled with ev_stat and large file support. |
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1684 | |
|
|
1685 | The solution for this is to lobby your distribution maker to make large |
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1686 | file interfaces available by default (as e.g. FreeBSD does) and not |
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1687 | optional. Libev cannot simply switch on large file support because it has |
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1688 | to exchange stat structures with application programs compiled using the |
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1689 | default compilation environment. |
1674 | |
1690 | |
1675 | =head3 Inotify |
1691 | =head3 Inotify |
1676 | |
1692 | |
1677 | When C<inotify (7)> support has been compiled into libev (generally only |
1693 | When C<inotify (7)> support has been compiled into libev (generally only |
1678 | available on Linux) and present at runtime, it will be used to speed up |
1694 | available on Linux) and present at runtime, it will be used to speed up |
… | |
… | |
3182 | parallel from multiple threads, calls with the same loop parameter must be |
3198 | parallel from multiple threads, calls with the same loop parameter must be |
3183 | done serially (but can be done from different threads, as long as only one |
3199 | done serially (but can be done from different threads, as long as only one |
3184 | thread ever is inside a call at any point in time, e.g. by using a mutex |
3200 | thread ever is inside a call at any point in time, e.g. by using a mutex |
3185 | per loop). |
3201 | per loop). |
3186 | |
3202 | |
3187 | If you want to know which design is best for your problem, then I cannot |
3203 | If you want to know which design (one loop, locking, or multiple loops |
3188 | help you but by giving some generic advice: |
3204 | without or something else still) is best for your problem, then I cannot |
|
|
3205 | help you. I can give some generic advice however: |
3189 | |
3206 | |
3190 | =over 4 |
3207 | =over 4 |
3191 | |
3208 | |
3192 | =item * most applications have a main thread: use the default libev loop |
3209 | =item * most applications have a main thread: use the default libev loop |
3193 | in that thread, or create a separate thread running only the default loop. |
3210 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3332 | section for details) and use the following F<evwrap.h> header file instead |
3349 | section for details) and use the following F<evwrap.h> header file instead |
3333 | of F<ev.h>: |
3350 | of F<ev.h>: |
3334 | |
3351 | |
3335 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
3352 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
3336 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3353 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3337 | #define EV_STAT_ENABLE 0 /* no stat() availble */ |
|
|
3338 | |
3354 | |
3339 | #include "ev.h" |
3355 | #include "ev.h" |
3340 | |
3356 | |
3341 | And compile the following F<evwrap.c> file into your project (make sure |
3357 | And compile the following F<evwrap.c> file into your project (make sure |
3342 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
3358 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |