… | |
… | |
620 | happily wraps around with enough iterations. |
620 | happily wraps around with enough iterations. |
621 | |
621 | |
622 | This value can sometimes be useful as a generation counter of sorts (it |
622 | This 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 |
624 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
|
|
625 | |
|
|
626 | =item unsigned int ev_loop_depth (loop) |
|
|
627 | |
|
|
628 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
630 | |
|
|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
633 | in which case it is higher. |
|
|
634 | |
|
|
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
636 | etc.), doesn't count as exit. |
625 | |
637 | |
626 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
627 | |
639 | |
628 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
629 | use. |
641 | use. |
… | |
… | |
811 | |
823 | |
812 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | By setting a higher I<io collect interval> you allow libev to spend more |
813 | time collecting I/O events, so you can handle more events per iteration, |
825 | time collecting I/O events, so you can handle more events per iteration, |
814 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
826 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
815 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
827 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
816 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
817 | |
831 | |
818 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
819 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
820 | latency/jitter/inexactness (the watcher callback will be called |
834 | latency/jitter/inexactness (the watcher callback will be called |
821 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
823 | |
837 | |
824 | Many (busy) programs can usually benefit by setting the I/O collect |
838 | Many (busy) programs can usually benefit by setting the I/O collect |
825 | interval to a value near C<0.1> or so, which is often enough for |
839 | interval to a value near C<0.1> or so, which is often enough for |
826 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
827 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
841 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
828 | as this approaches the timing granularity of most systems. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
829 | |
847 | |
830 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
831 | saving power, as the program will "bundle" timer callback invocations that |
849 | saving power, as the program will "bundle" timer callback invocations that |
832 | are "near" in time together, by delaying some, thus reducing the number of |
850 | are "near" in time together, by delaying some, thus reducing the number of |
833 | times the process sleeps and wakes up again. Another useful technique to |
851 | times the process sleeps and wakes up again. Another useful technique to |
834 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
835 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
|
|
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more 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 | |
839 | This function only does something when C<EV_VERIFY> support has been |
863 | This function only does something when C<EV_VERIFY> support has been |
840 | compiled in, which is the default for non-minimal builds. It tries to go |
864 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
1184 | #include <stddef.h> |
1208 | #include <stddef.h> |
1185 | |
1209 | |
1186 | static void |
1210 | static void |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1211 | t1_cb (EV_P_ ev_timer *w, int revents) |
1188 | { |
1212 | { |
1189 | struct my_biggy big = (struct my_biggy * |
1213 | struct my_biggy big = (struct my_biggy *) |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1214 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1191 | } |
1215 | } |
1192 | |
1216 | |
1193 | static void |
1217 | static void |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1218 | t2_cb (EV_P_ ev_timer *w, int revents) |
1195 | { |
1219 | { |
1196 | struct my_biggy big = (struct my_biggy * |
1220 | struct my_biggy big = (struct my_biggy *) |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1221 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1198 | } |
1222 | } |
1199 | |
1223 | |
1200 | =head2 WATCHER PRIORITY MODELS |
1224 | =head2 WATCHER PRIORITY MODELS |
1201 | |
1225 | |
… | |
… | |
1277 | // with the default priority are receiving events. |
1301 | // with the default priority are receiving events. |
1278 | ev_idle_start (EV_A_ &idle); |
1302 | ev_idle_start (EV_A_ &idle); |
1279 | } |
1303 | } |
1280 | |
1304 | |
1281 | static void |
1305 | static void |
1282 | idle-cb (EV_P_ ev_idle *w, int revents) |
1306 | idle_cb (EV_P_ ev_idle *w, int revents) |
1283 | { |
1307 | { |
1284 | // actual processing |
1308 | // actual processing |
1285 | read (STDIN_FILENO, ...); |
1309 | read (STDIN_FILENO, ...); |
1286 | |
1310 | |
1287 | // have to start the I/O watcher again, as |
1311 | // have to start the I/O watcher again, as |
… | |
… | |
1468 | |
1492 | |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1493 | The callback is guaranteed to be invoked only I<after> its timeout has |
1470 | passed (not I<at>, so on systems with very low-resolution clocks this |
1494 | passed (not I<at>, so on systems with very low-resolution clocks this |
1471 | might introduce a small delay). If multiple timers become ready during the |
1495 | might introduce a small delay). If multiple timers become ready during the |
1472 | same loop iteration then the ones with earlier time-out values are invoked |
1496 | same loop iteration then the ones with earlier time-out values are invoked |
1473 | before ones with later time-out values (but this is no longer true when a |
1497 | before ones of the same priority with later time-out values (but this is |
1474 | callback calls C<ev_loop> recursively). |
1498 | no longer true when a callback calls C<ev_loop> recursively). |
1475 | |
1499 | |
1476 | =head3 Be smart about timeouts |
1500 | =head3 Be smart about timeouts |
1477 | |
1501 | |
1478 | Many real-world problems involve some kind of timeout, usually for error |
1502 | Many real-world problems involve some kind of timeout, usually for error |
1479 | recovery. A typical example is an HTTP request - if the other side hangs, |
1503 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1523 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1547 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1524 | member and C<ev_timer_again>. |
1548 | member and C<ev_timer_again>. |
1525 | |
1549 | |
1526 | At start: |
1550 | At start: |
1527 | |
1551 | |
1528 | ev_timer_init (timer, callback); |
1552 | ev_init (timer, callback); |
1529 | timer->repeat = 60.; |
1553 | timer->repeat = 60.; |
1530 | ev_timer_again (loop, timer); |
1554 | ev_timer_again (loop, timer); |
1531 | |
1555 | |
1532 | Each time there is some activity: |
1556 | Each time there is some activity: |
1533 | |
1557 | |
… | |
… | |
1595 | |
1619 | |
1596 | To start the timer, simply initialise the watcher and set C<last_activity> |
1620 | To start the timer, simply initialise the watcher and set C<last_activity> |
1597 | to the current time (meaning we just have some activity :), then call the |
1621 | to the current time (meaning we just have some activity :), then call the |
1598 | callback, which will "do the right thing" and start the timer: |
1622 | callback, which will "do the right thing" and start the timer: |
1599 | |
1623 | |
1600 | ev_timer_init (timer, callback); |
1624 | ev_init (timer, callback); |
1601 | last_activity = ev_now (loop); |
1625 | last_activity = ev_now (loop); |
1602 | callback (loop, timer, EV_TIMEOUT); |
1626 | callback (loop, timer, EV_TIMEOUT); |
1603 | |
1627 | |
1604 | And when there is some activity, simply store the current time in |
1628 | And when there is some activity, simply store the current time in |
1605 | C<last_activity>, no libev calls at all: |
1629 | C<last_activity>, no libev calls at all: |
… | |
… | |
2002 | some child status changes (most typically when a child of yours dies or |
2026 | some child status changes (most typically when a child of yours dies or |
2003 | exits). It is permissible to install a child watcher I<after> the child |
2027 | exits). It is permissible to install a child watcher I<after> the child |
2004 | has been forked (which implies it might have already exited), as long |
2028 | has been forked (which implies it might have already exited), as long |
2005 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2029 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2006 | forking and then immediately registering a watcher for the child is fine, |
2030 | forking and then immediately registering a watcher for the child is fine, |
2007 | but forking and registering a watcher a few event loop iterations later is |
2031 | but forking and registering a watcher a few event loop iterations later or |
2008 | not. |
2032 | in the next callback invocation is not. |
2009 | |
2033 | |
2010 | Only the default event loop is capable of handling signals, and therefore |
2034 | Only the default event loop is capable of handling signals, and therefore |
2011 | you can only register child watchers in the default event loop. |
2035 | you can only register child watchers in the default event loop. |
|
|
2036 | |
|
|
2037 | Due to some design glitches inside libev, child watchers will always be |
|
|
2038 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2039 | libev) |
2012 | |
2040 | |
2013 | =head3 Process Interaction |
2041 | =head3 Process Interaction |
2014 | |
2042 | |
2015 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2043 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2016 | initialised. This is necessary to guarantee proper behaviour even if |
2044 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
2368 | // no longer anything immediate to do. |
2396 | // no longer anything immediate to do. |
2369 | } |
2397 | } |
2370 | |
2398 | |
2371 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2399 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2372 | ev_idle_init (idle_watcher, idle_cb); |
2400 | ev_idle_init (idle_watcher, idle_cb); |
2373 | ev_idle_start (loop, idle_cb); |
2401 | ev_idle_start (loop, idle_watcher); |
2374 | |
2402 | |
2375 | |
2403 | |
2376 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2404 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2377 | |
2405 | |
2378 | Prepare and check watchers are usually (but not always) used in pairs: |
2406 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2471 | struct pollfd fds [nfd]; |
2499 | struct pollfd fds [nfd]; |
2472 | // actual code will need to loop here and realloc etc. |
2500 | // actual code will need to loop here and realloc etc. |
2473 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2501 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2474 | |
2502 | |
2475 | /* the callback is illegal, but won't be called as we stop during check */ |
2503 | /* the callback is illegal, but won't be called as we stop during check */ |
2476 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2504 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2477 | ev_timer_start (loop, &tw); |
2505 | ev_timer_start (loop, &tw); |
2478 | |
2506 | |
2479 | // create one ev_io per pollfd |
2507 | // create one ev_io per pollfd |
2480 | for (int i = 0; i < nfd; ++i) |
2508 | for (int i = 0; i < nfd; ++i) |
2481 | { |
2509 | { |
… | |
… | |
3643 | defined to be C<0>, then they are not. |
3671 | defined to be C<0>, then they are not. |
3644 | |
3672 | |
3645 | =item EV_MINIMAL |
3673 | =item EV_MINIMAL |
3646 | |
3674 | |
3647 | If you need to shave off some kilobytes of code at the expense of some |
3675 | If you need to shave off some kilobytes of code at the expense of some |
3648 | speed, define this symbol to C<1>. Currently this is used to override some |
3676 | speed (but with the full API), define this symbol to C<1>. Currently this |
3649 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3677 | is used to override some inlining decisions, saves roughly 30% code size |
3650 | much smaller 2-heap for timer management over the default 4-heap. |
3678 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3679 | the default 4-heap. |
|
|
3680 | |
|
|
3681 | You can save even more by disabling watcher types you do not need and |
|
|
3682 | setting C<EV_MAXPRI> == C<EV_MINPRI>. |
3651 | |
3683 | |
3652 | =item EV_PID_HASHSIZE |
3684 | =item EV_PID_HASHSIZE |
3653 | |
3685 | |
3654 | C<ev_child> watchers use a small hash table to distribute workload by |
3686 | C<ev_child> watchers use a small hash table to distribute workload by |
3655 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3687 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3935 | way (note also that glib is the slowest event library known to man). |
3967 | way (note also that glib is the slowest event library known to man). |
3936 | |
3968 | |
3937 | There is no supported compilation method available on windows except |
3969 | There is no supported compilation method available on windows except |
3938 | embedding it into other applications. |
3970 | embedding it into other applications. |
3939 | |
3971 | |
|
|
3972 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3973 | tries its best, but under most conditions, signals will simply not work. |
|
|
3974 | |
3940 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3975 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3941 | accept large writes: instead of resulting in a partial write, windows will |
3976 | accept large writes: instead of resulting in a partial write, windows will |
3942 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3977 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3943 | so make sure you only write small amounts into your sockets (less than a |
3978 | so make sure you only write small amounts into your sockets (less than a |
3944 | megabyte seems safe, but this apparently depends on the amount of memory |
3979 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3948 | the abysmal performance of winsockets, using a large number of sockets |
3983 | the abysmal performance of winsockets, using a large number of sockets |
3949 | is not recommended (and not reasonable). If your program needs to use |
3984 | is not recommended (and not reasonable). If your program needs to use |
3950 | more than a hundred or so sockets, then likely it needs to use a totally |
3985 | more than a hundred or so sockets, then likely it needs to use a totally |
3951 | different implementation for windows, as libev offers the POSIX readiness |
3986 | different implementation for windows, as libev offers the POSIX readiness |
3952 | notification model, which cannot be implemented efficiently on windows |
3987 | notification model, which cannot be implemented efficiently on windows |
3953 | (Microsoft monopoly games). |
3988 | (due to Microsoft monopoly games). |
3954 | |
3989 | |
3955 | A typical way to use libev under windows is to embed it (see the embedding |
3990 | A typical way to use libev under windows is to embed it (see the embedding |
3956 | section for details) and use the following F<evwrap.h> header file instead |
3991 | section for details) and use the following F<evwrap.h> header file instead |
3957 | of F<ev.h>: |
3992 | of F<ev.h>: |
3958 | |
3993 | |
… | |
… | |
3994 | |
4029 | |
3995 | Early versions of winsocket's select only supported waiting for a maximum |
4030 | Early versions of winsocket's select only supported waiting for a maximum |
3996 | of C<64> handles (probably owning to the fact that all windows kernels |
4031 | of C<64> handles (probably owning to the fact that all windows kernels |
3997 | can only wait for C<64> things at the same time internally; Microsoft |
4032 | can only wait for C<64> things at the same time internally; Microsoft |
3998 | recommends spawning a chain of threads and wait for 63 handles and the |
4033 | recommends spawning a chain of threads and wait for 63 handles and the |
3999 | previous thread in each. Great). |
4034 | previous thread in each. Sounds great!). |
4000 | |
4035 | |
4001 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4036 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4002 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4037 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4003 | call (which might be in libev or elsewhere, for example, perl does its own |
4038 | call (which might be in libev or elsewhere, for example, perl and many |
4004 | select emulation on windows). |
4039 | other interpreters do their own select emulation on windows). |
4005 | |
4040 | |
4006 | Another limit is the number of file descriptors in the Microsoft runtime |
4041 | Another limit is the number of file descriptors in the Microsoft runtime |
4007 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4042 | libraries, which by default is C<64> (there must be a hidden I<64> |
4008 | or something like this inside Microsoft). You can increase this by calling |
4043 | fetish or something like this inside Microsoft). You can increase this |
4009 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4044 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
4010 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4045 | (another arbitrary limit), but is broken in many versions of the Microsoft |
4011 | libraries. |
|
|
4012 | |
|
|
4013 | This might get you to about C<512> or C<2048> sockets (depending on |
4046 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4014 | windows version and/or the phase of the moon). To get more, you need to |
4047 | (depending on windows version and/or the phase of the moon). To get more, |
4015 | wrap all I/O functions and provide your own fd management, but the cost of |
4048 | you need to wrap all I/O functions and provide your own fd management, but |
4016 | calling select (O(n²)) will likely make this unworkable. |
4049 | the cost of calling select (O(n²)) will likely make this unworkable. |
4017 | |
4050 | |
4018 | =back |
4051 | =back |
4019 | |
4052 | |
4020 | =head2 PORTABILITY REQUIREMENTS |
4053 | =head2 PORTABILITY REQUIREMENTS |
4021 | |
4054 | |
… | |
… | |
4064 | =item C<double> must hold a time value in seconds with enough accuracy |
4097 | =item C<double> must hold a time value in seconds with enough accuracy |
4065 | |
4098 | |
4066 | The type C<double> is used to represent timestamps. It is required to |
4099 | The type C<double> is used to represent timestamps. It is required to |
4067 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4100 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4068 | enough for at least into the year 4000. This requirement is fulfilled by |
4101 | enough for at least into the year 4000. This requirement is fulfilled by |
4069 | implementations implementing IEEE 754 (basically all existing ones). |
4102 | implementations implementing IEEE 754, which is basically all existing |
|
|
4103 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4104 | 2200. |
4070 | |
4105 | |
4071 | =back |
4106 | =back |
4072 | |
4107 | |
4073 | If you know of other additional requirements drop me a note. |
4108 | If you know of other additional requirements drop me a note. |
4074 | |
4109 | |