… | |
… | |
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 |
… | |
… | |
511 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
515 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
512 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
516 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
513 | |
517 | |
514 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
518 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
515 | |
519 | |
516 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
520 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
517 | kernels). |
521 | kernels). |
518 | |
522 | |
519 | For few fds, this backend is a bit little slower than poll and select, but |
523 | 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 |
524 | 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 |
525 | 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 |
578 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
575 | C<EVBACKEND_POLL>. |
579 | C<EVBACKEND_POLL>. |
576 | |
580 | |
577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
581 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
578 | |
582 | |
579 | Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<< |
583 | 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. |
584 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
|
|
585 | only tries to use it in 4.19+). |
|
|
586 | |
|
|
587 | This is another Linux train wreck of an event interface. |
581 | |
588 | |
582 | If this backend works for you (as of this writing, it was very |
589 | 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 |
590 | 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 |
591 | be well worth enabling it - if it isn't available in your kernel this will |
585 | be detected and this backend will be skipped. |
592 | be detected and this backend will be skipped. |
586 | |
593 | |
587 | This backend can batch oneshot requests and supports a user-space ring |
594 | 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 |
595 | 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 |
596 | 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 |
597 | 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 |
598 | being the Linux kernel, of course it suffers from a whole new set of |
592 | limitations. |
599 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
600 | issues. |
593 | |
601 | |
594 | For one, it is not easily embeddable (but probably could be done using |
602 | 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 |
603 | 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 |
604 | 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. |
605 | requests are left, this backend will be skipped during initialisation, and |
|
|
606 | will switch to epoll when the loop is active. |
599 | |
607 | |
600 | Most problematic in practise, however, is that not all file descriptors |
608 | 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, |
609 | 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 |
610 | files, F</dev/null> and many others are supported, but ttys do not work |
603 | (probably because of a bug), so this is not (yet?) a generic event polling |
611 | properly (a known bug that the kernel developers don't care about, see |
604 | interface. |
612 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
613 | (yet?) a generic event polling interface. |
605 | |
614 | |
|
|
615 | Overall, it seems the Linux developers just don't want it to have a |
|
|
616 | generic event handling mechanism other than C<select> or C<poll>. |
|
|
617 | |
606 | To work around this latter problem, the current version of libev uses |
618 | To work around all these problem, the current version of libev uses its |
607 | epoll as a fallback for file deescriptor types that do not work. Epoll |
619 | epoll backend as a fallback for file descriptor types that do not work. Or |
608 | is used in, kind of, slow mode that hopefully avoids most of its design |
620 | falls back completely to epoll if the kernel acts up. |
609 | problems and requires 1-3 extra syscalls per active fd every iteration. |
|
|
610 | |
621 | |
611 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
622 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
612 | C<EVBACKEND_POLL>. |
623 | C<EVBACKEND_POLL>. |
613 | |
624 | |
614 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
625 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
615 | |
626 | |
616 | Kqueue deserves special mention, as at the time of this writing, it |
627 | Kqueue deserves special mention, as at the time this backend was |
617 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
628 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
618 | with anything but sockets and pipes, except on Darwin, where of course |
629 | work reliably with anything but sockets and pipes, except on Darwin, |
619 | it's completely useless). Unlike epoll, however, whose brokenness |
630 | where of course it's completely useless). Unlike epoll, however, whose |
620 | is by design, these kqueue bugs can (and eventually will) be fixed |
631 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
621 | without API changes to existing programs. For this reason it's not being |
632 | fixed without API changes to existing programs. For this reason it's not |
622 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
633 | being "auto-detected" on all platforms unless you explicitly specify it |
623 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
634 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
624 | system like NetBSD. |
635 | known-to-be-good (-enough) system like NetBSD. |
625 | |
636 | |
626 | You still can embed kqueue into a normal poll or select backend and use it |
637 | You still can embed kqueue into a normal poll or select backend and use it |
627 | only for sockets (after having made sure that sockets work with kqueue on |
638 | only for sockets (after having made sure that sockets work with kqueue on |
628 | the target platform). See C<ev_embed> watchers for more info. |
639 | the target platform). See C<ev_embed> watchers for more info. |
629 | |
640 | |
630 | It scales in the same way as the epoll backend, but the interface to the |
641 | It scales in the same way as the epoll backend, but the interface to the |
631 | kernel is more efficient (which says nothing about its actual speed, of |
642 | kernel is more efficient (which says nothing about its actual speed, of |
632 | course). While stopping, setting and starting an I/O watcher does never |
643 | course). While stopping, setting and starting an I/O watcher does never |
633 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
644 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
634 | two event changes per incident. Support for C<fork ()> is very bad (you |
645 | two event changes per incident. Support for C<fork ()> is very bad (you |
635 | might have to leak fd's on fork, but it's more sane than epoll) and it |
646 | might have to leak fds on fork, but it's more sane than epoll) and it |
636 | drops fds silently in similarly hard-to-detect cases. |
647 | drops fds silently in similarly hard-to-detect cases. |
637 | |
648 | |
638 | This backend usually performs well under most conditions. |
649 | This backend usually performs well under most conditions. |
639 | |
650 | |
640 | While nominally embeddable in other event loops, this doesn't work |
651 | While nominally embeddable in other event loops, this doesn't work |
… | |
… | |
1738 | when you rarely read from a file instead of from a socket, and want to |
1749 | when you rarely read from a file instead of from a socket, and want to |
1739 | reuse the same code path. |
1750 | reuse the same code path. |
1740 | |
1751 | |
1741 | =head3 The special problem of fork |
1752 | =head3 The special problem of fork |
1742 | |
1753 | |
1743 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1754 | Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()> |
1744 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1755 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1745 | to be told about it in the child if you want to continue to use it in the |
1756 | to be told about it in the child if you want to continue to use it in the |
1746 | child. |
1757 | child. |
1747 | |
1758 | |
1748 | To support fork in your child processes, you have to call C<ev_loop_fork |
1759 | To support fork in your child processes, you have to call C<ev_loop_fork |
… | |
… | |
4473 | |
4484 | |
4474 | ev_select.c only when select backend is enabled |
4485 | ev_select.c only when select backend is enabled |
4475 | ev_poll.c only when poll backend is enabled |
4486 | ev_poll.c only when poll backend is enabled |
4476 | ev_epoll.c only when the epoll backend is enabled |
4487 | ev_epoll.c only when the epoll backend is enabled |
4477 | ev_linuxaio.c only when the linux aio backend is enabled |
4488 | ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4489 | ev_iouring.c only when the linux io_uring backend is enabled |
4478 | ev_kqueue.c only when the kqueue backend is enabled |
4490 | ev_kqueue.c only when the kqueue backend is enabled |
4479 | ev_port.c only when the solaris port backend is enabled |
4491 | ev_port.c only when the solaris port backend is enabled |
4480 | |
4492 | |
4481 | F<ev.c> includes the backend files directly when enabled, so you only need |
4493 | F<ev.c> includes the backend files directly when enabled, so you only need |
4482 | to compile this single file. |
4494 | to compile this single file. |
… | |
… | |
4675 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4687 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4676 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4688 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4677 | |
4689 | |
4678 | =item EV_USE_LINUXAIO |
4690 | =item EV_USE_LINUXAIO |
4679 | |
4691 | |
|
|
4692 | If defined to be C<1>, libev will compile in support for the Linux aio |
|
|
4693 | backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be |
|
|
4694 | enabled on linux, otherwise disabled. |
|
|
4695 | |
|
|
4696 | =item EV_USE_IOURING |
|
|
4697 | |
4680 | If defined to be C<1>, libev will compile in support for the Linux |
4698 | If defined to be C<1>, libev will compile in support for the Linux |
4681 | aio backend. Due to it's currenbt limitations it has to be requested |
4699 | io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's |
4682 | explicitly. If undefined, it will be enabled on linux, otherwise |
4700 | current limitations it has to be requested explicitly. If undefined, it |
4683 | disabled. |
4701 | will be enabled on linux, otherwise disabled. |
4684 | |
4702 | |
4685 | =item EV_USE_KQUEUE |
4703 | =item EV_USE_KQUEUE |
4686 | |
4704 | |
4687 | If defined to be C<1>, libev will compile in support for the BSD style |
4705 | If defined to be C<1>, libev will compile in support for the BSD style |
4688 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4706 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4966 | called. If set to C<2>, then the internal verification code will be |
4984 | called. If set to C<2>, then the internal verification code will be |
4967 | called once per loop, which can slow down libev. If set to C<3>, then the |
4985 | called once per loop, which can slow down libev. If set to C<3>, then the |
4968 | verification code will be called very frequently, which will slow down |
4986 | verification code will be called very frequently, which will slow down |
4969 | libev considerably. |
4987 | libev considerably. |
4970 | |
4988 | |
|
|
4989 | Verification errors are reported via C's C<assert> mechanism, so if you |
|
|
4990 | disable that (e.g. by defining C<NDEBUG>) then no errors will be reported. |
|
|
4991 | |
4971 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4992 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4972 | will be C<0>. |
4993 | will be C<0>. |
4973 | |
4994 | |
4974 | =item EV_COMMON |
4995 | =item EV_COMMON |
4975 | |
4996 | |