… | |
… | |
159 | When libev detects a usage error such as a negative timer interval, then |
159 | When libev detects a usage error such as a negative timer interval, then |
160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
161 | so C<NDEBUG> will disable this checking): these are programming errors in |
161 | so C<NDEBUG> will disable this checking): these are programming errors in |
162 | the libev caller and need to be fixed there. |
162 | the libev caller and need to be fixed there. |
163 | |
163 | |
|
|
164 | Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive |
|
|
165 | consistency checking code inside libev that can be used to check for |
|
|
166 | internal inconsistencies, suually caused by application bugs. |
|
|
167 | |
164 | Libev also has a few internal error-checking C<assert>ions, and also has |
168 | Libev also has a few internal error-checking C<assert>ions. These do not |
165 | extensive consistency checking code. These do not trigger under normal |
|
|
166 | circumstances, as they indicate either a bug in libev or worse. |
169 | trigger under normal circumstances, as they indicate either a bug in libev |
|
|
170 | or worse. |
167 | |
171 | |
168 | |
172 | |
169 | =head1 GLOBAL FUNCTIONS |
173 | =head1 GLOBAL FUNCTIONS |
170 | |
174 | |
171 | These functions can be called anytime, even before initialising the |
175 | These functions can be called anytime, even before initialising the |
… | |
… | |
476 | unblocking the signals. |
480 | unblocking the signals. |
477 | |
481 | |
478 | It's also required by POSIX in a threaded program, as libev calls |
482 | It's also required by POSIX in a threaded program, as libev calls |
479 | C<sigprocmask>, whose behaviour is officially unspecified. |
483 | C<sigprocmask>, whose behaviour is officially unspecified. |
480 | |
484 | |
481 | This flag's behaviour will become the default in future versions of libev. |
485 | =item C<EVFLAG_NOTIMERFD> |
|
|
486 | |
|
|
487 | When this flag is specified, the libev will avoid using a C<timerfd> to |
|
|
488 | detect time jumps. It will still be able to detect time jumps, but takes |
|
|
489 | longer and has a lower accuracy in doing so, but saves a file descriptor |
|
|
490 | per loop. |
|
|
491 | |
|
|
492 | The current implementation only tries to use a C<timerfd> when the first |
|
|
493 | C<ev_periodic> watcher is started and falls back on other methods if it |
|
|
494 | cannot be created, but this behaviour might change in the future. |
482 | |
495 | |
483 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
496 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
484 | |
497 | |
485 | This is your standard select(2) backend. Not I<completely> standard, as |
498 | This is your standard select(2) backend. Not I<completely> standard, as |
486 | libev tries to roll its own fd_set with no limits on the number of fds, |
499 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
511 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
524 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
512 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
525 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
513 | |
526 | |
514 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
527 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
515 | |
528 | |
516 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
529 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
517 | kernels). |
530 | kernels). |
518 | |
531 | |
519 | For few fds, this backend is a bit little slower than poll and select, but |
532 | For few fds, this backend is a bit little slower than poll and select, but |
520 | it scales phenomenally better. While poll and select usually scale like |
533 | it scales phenomenally better. While poll and select usually scale like |
521 | O(total_fds) where total_fds is the total number of fds (or the highest |
534 | O(total_fds) where total_fds is the total number of fds (or the highest |
… | |
… | |
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
587 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
575 | C<EVBACKEND_POLL>. |
588 | C<EVBACKEND_POLL>. |
576 | |
589 | |
577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
590 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
578 | |
591 | |
579 | Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<< |
592 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
580 | io_submit(2) >>) event interface available in post-4.18 kernels. |
593 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
|
|
594 | only tries to use it in 4.19+). |
|
|
595 | |
|
|
596 | This is another Linux train wreck of an event interface. |
581 | |
597 | |
582 | If this backend works for you (as of this writing, it was very |
598 | If this backend works for you (as of this writing, it was very |
583 | experimental), it is the best event interface available on linux and might |
599 | experimental), it is the best event interface available on Linux and might |
584 | be well worth enabling it - if it isn't available in your kernel this will |
600 | be well worth enabling it - if it isn't available in your kernel this will |
585 | be detected and this backend will be skipped. |
601 | be detected and this backend will be skipped. |
586 | |
602 | |
587 | This backend can batch oneshot requests and supports a user-space ring |
603 | This backend can batch oneshot requests and supports a user-space ring |
588 | buffer to receive events. It also doesn't suffer from most of the design |
604 | buffer to receive events. It also doesn't suffer from most of the design |
589 | problems of epoll (such as not being able to remove event sources from |
605 | problems of epoll (such as not being able to remove event sources from |
590 | the epoll set), and generally sounds too good to be true. Because, this |
606 | the epoll set), and generally sounds too good to be true. Because, this |
591 | being the linux kernel, of course it suffers from a whole new set of |
607 | being the Linux kernel, of course it suffers from a whole new set of |
592 | limitations. |
608 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
609 | issues. |
593 | |
610 | |
594 | For one, it is not easily embeddable (but probably could be done using |
611 | For one, it is not easily embeddable (but probably could be done using |
595 | an event fd at some extra overhead). It also is subject to a system wide |
612 | an event fd at some extra overhead). It also is subject to a system wide |
596 | limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop |
613 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
597 | currently requires C<61> of this number. If no aio requests are left, this |
|
|
598 | backend will be skipped during initialisation. |
614 | requests are left, this backend will be skipped during initialisation, and |
|
|
615 | will switch to epoll when the loop is active. |
599 | |
616 | |
600 | Most problematic in practise, however, is that not all file descriptors |
617 | Most problematic in practice, however, is that not all file descriptors |
601 | work with it. For example, in linux 5.1, tcp sockets, pipes, event fds, |
618 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
602 | files, F</dev/null> and a few others are supported, but ttys do not work |
619 | files, F</dev/null> and many others are supported, but ttys do not work |
603 | properly (a known bug that the kernel developers don't care about, see |
620 | properly (a known bug that the kernel developers don't care about, see |
604 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
621 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
605 | (yet?) a generic event polling interface. |
622 | (yet?) a generic event polling interface. |
606 | |
623 | |
|
|
624 | Overall, it seems the Linux developers just don't want it to have a |
|
|
625 | generic event handling mechanism other than C<select> or C<poll>. |
|
|
626 | |
607 | To work around this latter problem, the current version of libev uses |
627 | To work around all these problem, the current version of libev uses its |
608 | epoll as a fallback for file deescriptor types that do not work. Epoll |
628 | epoll backend as a fallback for file descriptor types that do not work. Or |
609 | is used in, kind of, slow mode that hopefully avoids most of its design |
629 | falls back completely to epoll if the kernel acts up. |
610 | problems and requires 1-3 extra syscalls per active fd every iteration. |
|
|
611 | |
630 | |
612 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
631 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
613 | C<EVBACKEND_POLL>. |
632 | C<EVBACKEND_POLL>. |
614 | |
633 | |
615 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
634 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
616 | |
635 | |
617 | Kqueue deserves special mention, as at the time of this writing, it |
636 | Kqueue deserves special mention, as at the time this backend was |
618 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
637 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
619 | with anything but sockets and pipes, except on Darwin, where of course |
638 | work reliably with anything but sockets and pipes, except on Darwin, |
620 | it's completely useless). Unlike epoll, however, whose brokenness |
639 | where of course it's completely useless). Unlike epoll, however, whose |
621 | is by design, these kqueue bugs can (and eventually will) be fixed |
640 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
622 | without API changes to existing programs. For this reason it's not being |
641 | fixed without API changes to existing programs. For this reason it's not |
623 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
642 | being "auto-detected" on all platforms unless you explicitly specify it |
624 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
643 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
625 | system like NetBSD. |
644 | known-to-be-good (-enough) system like NetBSD. |
626 | |
645 | |
627 | You still can embed kqueue into a normal poll or select backend and use it |
646 | You still can embed kqueue into a normal poll or select backend and use it |
628 | only for sockets (after having made sure that sockets work with kqueue on |
647 | only for sockets (after having made sure that sockets work with kqueue on |
629 | the target platform). See C<ev_embed> watchers for more info. |
648 | the target platform). See C<ev_embed> watchers for more info. |
630 | |
649 | |
631 | It scales in the same way as the epoll backend, but the interface to the |
650 | It scales in the same way as the epoll backend, but the interface to the |
632 | kernel is more efficient (which says nothing about its actual speed, of |
651 | kernel is more efficient (which says nothing about its actual speed, of |
633 | course). While stopping, setting and starting an I/O watcher does never |
652 | course). While stopping, setting and starting an I/O watcher does never |
634 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
653 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
635 | two event changes per incident. Support for C<fork ()> is very bad (you |
654 | two event changes per incident. Support for C<fork ()> is very bad (you |
636 | might have to leak fd's on fork, but it's more sane than epoll) and it |
655 | might have to leak fds on fork, but it's more sane than epoll) and it |
637 | drops fds silently in similarly hard-to-detect cases. |
656 | drops fds silently in similarly hard-to-detect cases. |
638 | |
657 | |
639 | This backend usually performs well under most conditions. |
658 | This backend usually performs well under most conditions. |
640 | |
659 | |
641 | While nominally embeddable in other event loops, this doesn't work |
660 | While nominally embeddable in other event loops, this doesn't work |
… | |
… | |
1525 | |
1544 | |
1526 | Many event loops support I<watcher priorities>, which are usually small |
1545 | Many event loops support I<watcher priorities>, which are usually small |
1527 | integers that influence the ordering of event callback invocation |
1546 | integers that influence the ordering of event callback invocation |
1528 | between watchers in some way, all else being equal. |
1547 | between watchers in some way, all else being equal. |
1529 | |
1548 | |
1530 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
1549 | In libev, watcher priorities can be set using C<ev_set_priority>. See its |
1531 | description for the more technical details such as the actual priority |
1550 | description for the more technical details such as the actual priority |
1532 | range. |
1551 | range. |
1533 | |
1552 | |
1534 | There are two common ways how these these priorities are being interpreted |
1553 | There are two common ways how these these priorities are being interpreted |
1535 | by event loops: |
1554 | by event loops: |
… | |
… | |
1739 | when you rarely read from a file instead of from a socket, and want to |
1758 | when you rarely read from a file instead of from a socket, and want to |
1740 | reuse the same code path. |
1759 | reuse the same code path. |
1741 | |
1760 | |
1742 | =head3 The special problem of fork |
1761 | =head3 The special problem of fork |
1743 | |
1762 | |
1744 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1763 | Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()> |
1745 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1764 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1746 | to be told about it in the child if you want to continue to use it in the |
1765 | to be told about it in the child if you want to continue to use it in the |
1747 | child. |
1766 | child. |
1748 | |
1767 | |
1749 | To support fork in your child processes, you have to call C<ev_loop_fork |
1768 | To support fork in your child processes, you have to call C<ev_loop_fork |
… | |
… | |
4474 | |
4493 | |
4475 | ev_select.c only when select backend is enabled |
4494 | ev_select.c only when select backend is enabled |
4476 | ev_poll.c only when poll backend is enabled |
4495 | ev_poll.c only when poll backend is enabled |
4477 | ev_epoll.c only when the epoll backend is enabled |
4496 | ev_epoll.c only when the epoll backend is enabled |
4478 | ev_linuxaio.c only when the linux aio backend is enabled |
4497 | ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4498 | ev_iouring.c only when the linux io_uring backend is enabled |
4479 | ev_kqueue.c only when the kqueue backend is enabled |
4499 | ev_kqueue.c only when the kqueue backend is enabled |
4480 | ev_port.c only when the solaris port backend is enabled |
4500 | ev_port.c only when the solaris port backend is enabled |
4481 | |
4501 | |
4482 | F<ev.c> includes the backend files directly when enabled, so you only need |
4502 | F<ev.c> includes the backend files directly when enabled, so you only need |
4483 | to compile this single file. |
4503 | to compile this single file. |
… | |
… | |
4604 | available and will probe for kernel support at runtime. This will improve |
4624 | available and will probe for kernel support at runtime. This will improve |
4605 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4625 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4606 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4626 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4607 | 2.7 or newer, otherwise disabled. |
4627 | 2.7 or newer, otherwise disabled. |
4608 | |
4628 | |
|
|
4629 | =item EV_USE_SIGNALFD |
|
|
4630 | |
|
|
4631 | If defined to be C<1>, then libev will assume that C<signalfd ()> is |
|
|
4632 | available and will probe for kernel support at runtime. This enables |
|
|
4633 | the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If |
|
|
4634 | undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4635 | 2.7 or newer, otherwise disabled. |
|
|
4636 | |
|
|
4637 | =item EV_USE_TIMERFD |
|
|
4638 | |
|
|
4639 | If defined to be C<1>, then libev will assume that C<timerfd ()> is |
|
|
4640 | available and will probe for kernel support at runtime. This allows |
|
|
4641 | libev to detect time jumps accurately. If undefined, it will be enabled |
|
|
4642 | if the headers indicate GNU/Linux + Glibc 2.8 or newer and define |
|
|
4643 | C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled. |
|
|
4644 | |
|
|
4645 | =item EV_USE_EVENTFD |
|
|
4646 | |
|
|
4647 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
4648 | available and will probe for kernel support at runtime. This will improve |
|
|
4649 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
4650 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4651 | 2.7 or newer, otherwise disabled. |
|
|
4652 | |
4609 | =item EV_USE_SELECT |
4653 | =item EV_USE_SELECT |
4610 | |
4654 | |
4611 | If undefined or defined to be C<1>, libev will compile in support for the |
4655 | If undefined or defined to be C<1>, libev will compile in support for the |
4612 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4656 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4613 | other method takes over, select will be it. Otherwise the select backend |
4657 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
4676 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4720 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4677 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4721 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4678 | |
4722 | |
4679 | =item EV_USE_LINUXAIO |
4723 | =item EV_USE_LINUXAIO |
4680 | |
4724 | |
|
|
4725 | If defined to be C<1>, libev will compile in support for the Linux aio |
|
|
4726 | backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be |
|
|
4727 | enabled on linux, otherwise disabled. |
|
|
4728 | |
|
|
4729 | =item EV_USE_IOURING |
|
|
4730 | |
4681 | If defined to be C<1>, libev will compile in support for the Linux |
4731 | If defined to be C<1>, libev will compile in support for the Linux |
4682 | aio backend. Due to it's currenbt limitations it has to be requested |
4732 | io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's |
4683 | explicitly. If undefined, it will be enabled on linux, otherwise |
4733 | current limitations it has to be requested explicitly. If undefined, it |
4684 | disabled. |
4734 | will be enabled on linux, otherwise disabled. |
4685 | |
4735 | |
4686 | =item EV_USE_KQUEUE |
4736 | =item EV_USE_KQUEUE |
4687 | |
4737 | |
4688 | If defined to be C<1>, libev will compile in support for the BSD style |
4738 | If defined to be C<1>, libev will compile in support for the BSD style |
4689 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4739 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4967 | called. If set to C<2>, then the internal verification code will be |
5017 | called. If set to C<2>, then the internal verification code will be |
4968 | called once per loop, which can slow down libev. If set to C<3>, then the |
5018 | called once per loop, which can slow down libev. If set to C<3>, then the |
4969 | verification code will be called very frequently, which will slow down |
5019 | verification code will be called very frequently, which will slow down |
4970 | libev considerably. |
5020 | libev considerably. |
4971 | |
5021 | |
|
|
5022 | Verification errors are reported via C's C<assert> mechanism, so if you |
|
|
5023 | disable that (e.g. by defining C<NDEBUG>) then no errors will be reported. |
|
|
5024 | |
4972 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
5025 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4973 | will be C<0>. |
5026 | will be C<0>. |
4974 | |
5027 | |
4975 | =item EV_COMMON |
5028 | =item EV_COMMON |
4976 | |
5029 | |