--- libev/ev.3	2019/06/20 22:44:59	1.110
+++ libev/ev.3	2019/06/23 02:02:24	1.111
@@ -133,7 +133,7 @@
 .\" ========================================================================
 .\"
 .IX Title "LIBEV 3"
-.TH LIBEV 3 "2019-06-20" "libev-4.25" "libev - high performance full featured event loop"
+.TH LIBEV 3 "2019-06-22" "libev-4.25" "libev - high performance full featured event loop"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
@@ -242,10 +242,10 @@
 watcher.
 .SS "\s-1FEATURES\s0"
 .IX Subsection "FEATURES"
-Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
-BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
-for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
-(for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
+Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR
+interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port
+mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR
+interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
 inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
 timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
 (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
@@ -696,7 +696,40 @@
 the usage. So sad.
 .Sp
 While nominally embeddable in other event loops, this feature is broken in
-all kernel versions tested so far.
+a lot of kernel revisions, but probably(!) works in current versions.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
+.ie n .IP """EVBACKEND_LINUXAIO""   (value 64, Linux)" 4
+.el .IP "\f(CWEVBACKEND_LINUXAIO\fR   (value 64, Linux)" 4
+.IX Item "EVBACKEND_LINUXAIO (value 64, Linux)"
+Use the linux-specific linux aio (\fInot\fR \f(CWaio(7)\fR) event interface
+available in post\-4.18 kernels.
+.Sp
+If this backend works for you (as of this writing, it was very
+experimental and only supports a subset of file types), it is the best
+event interface available on linux and might be well worth it enabling it
+\&\- if it isn't available in your kernel this will be detected and another
+backend will be chosen.
+.Sp
+This backend can batch oneshot requests and uses a user-space ring buffer
+to receive events. It also doesn't suffer from most of the design problems
+of epoll (such as not being able to remove event sources from the epoll
+set), and generally sounds too good to be true. Because, this being the
+linux kernel, of course it suffers from a whole new set of limitations.
+.Sp
+For one, it is not easily embeddable (but probably could be done using
+an event fd at some extra overhead). It also is subject to various
+arbitrary limits that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR
+and \fI/proc/sys/fs/aio\-nr\fR), which could lead to it being skipped during
+initialisation.
+.Sp
+Most problematic in practise, however, is that, like kqueue, it requires
+special support from drivers, and, not surprisingly, not all drivers
+implement it. For example, in linux 4.19, tcp sockets, pipes, event fds,
+files, \fI/dev/null\fR and a few others are supported, but ttys are not, so
+this is not (yet?) a generic event polling interface but is probably still
+be very useful in a web server or similar program.
 .Sp
 This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
 \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
@@ -810,6 +843,14 @@
 .Vb 1
 \&   struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
 .Ve
+.Sp
+Example: Similarly, on linux, you mgiht want to take advantage of the
+linux aio backend if possible, but fall back to something else if that
+isn't available.
+.Sp
+.Vb 1
+\&   struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
+.Ve
 .RE
 .IP "ev_loop_destroy (loop)" 4
 .IX Item "ev_loop_destroy (loop)"
@@ -1750,13 +1791,13 @@
 \fIThe special problem of disappearing file descriptors\fR
 .IX Subsection "The special problem of disappearing file descriptors"
 .PP
-Some backends (e.g. kqueue, epoll) need to be told about closing a file
-descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means,
-such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file
-descriptor, but when it goes away, the operating system will silently drop
-this interest. If another file descriptor with the same number then is
-registered with libev, there is no efficient way to see that this is, in
-fact, a different file descriptor.
+Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
+a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other
+means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some
+file descriptor, but when it goes away, the operating system will silently
+drop this interest. If another file descriptor with the same number then
+is registered with libev, there is no efficient way to see that this is,
+in fact, a different file descriptor.
 .PP
 To avoid having to explicitly tell libev about such cases, libev follows
 the following policy:  Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
@@ -1818,9 +1859,10 @@
 \fIThe special problem of fork\fR
 .IX Subsection "The special problem of fork"
 .PP
-Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
-useless behaviour. Libev fully supports fork, but needs to be told about
-it in the child if you want to continue to use it in the child.
+Some backends (epoll, kqueue, probably linuxaio) do not support \f(CW\*(C`fork ()\*(C'\fR
+at all or exhibit useless behaviour. Libev fully supports fork, but needs
+to be told about it in the child if you want to continue to use it in the
+child.
 .PP
 To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
 ()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
@@ -4569,6 +4611,7 @@
 \&   ev_select.c     only when select backend is enabled
 \&   ev_poll.c       only when poll backend is enabled
 \&   ev_epoll.c      only when the epoll backend is enabled
+\&   ev_linuxaio.c   only when the linux aio backend is enabled
 \&   ev_kqueue.c     only when the kqueue backend is enabled
 \&   ev_port.c       only when the solaris port backend is enabled
 .Ve
@@ -4759,6 +4802,12 @@
 otherwise another method will be used as fallback. This is the preferred
 backend for GNU/Linux systems. If undefined, it will be enabled if the
 headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
+.IP "\s-1EV_USE_LINUXAIO\s0" 4
+.IX Item "EV_USE_LINUXAIO"
+If defined to be \f(CW1\fR, libev will compile in support for the Linux
+aio backend. Due to it's currenbt limitations it has to be requested
+explicitly.  If undefined, it will be enabled on linux, otherwise
+disabled.
 .IP "\s-1EV_USE_KQUEUE\s0" 4
 .IX Item "EV_USE_KQUEUE"
 If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style