- ein bild sagt mehr als tausend worte

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index ab0f5070c22a319e05fd94c4e06765cb7739bdc9..43db80f2552c54a983d830740eb3c51300efd07a 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -4,8 +4,48 @@ libev - a high performance full-featured event loop written in C
 
 =head1 SYNOPSIS
 
 
 =head1 SYNOPSIS
 

+  /* this is the only header you need */

   #include <ev.h>
 
   #include <ev.h>
 

+  /* what follows is a fully working example program */
+  ev_io stdin_watcher;
+  ev_timer timeout_watcher;
+
+  /* called when data readable on stdin */
+  static void
+  stdin_cb (EV_P_ struct ev_io *w, int revents)
+  {
+    /* puts ("stdin ready"); */
+    ev_io_stop (EV_A_ w); /* just a syntax example */
+    ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
+  }
+
+  static void
+  timeout_cb (EV_P_ struct ev_timer *w, int revents)
+  {
+    /* puts ("timeout"); */
+    ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
+  }
+
+  int
+  main (void)
+  {
+    struct ev_loop *loop = ev_default_loop (0);
+
+    /* initialise an io watcher, then start it */
+    ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+    ev_io_start (loop, &stdin_watcher);
+
+    /* simple non-repeating 5.5 second timeout */
+    ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+    ev_timer_start (loop, &timeout_watcher);
+
+    /* loop till timeout or data ready */
+    ev_loop (loop, 0);
+
+    return 0;
+  }
+

 =head1 DESCRIPTION
 
 Libev is an event loop: you register interest in certain events (such as a
 =head1 DESCRIPTION
 
 Libev is an event loop: you register interest in certain events (such as a


@@ -50,7 +90,6 @@ called C<ev_tstamp>, which is what you should use too. It usually aliases
 to the C<double> type in C, and when you need to do any calculations on
 it, you should treat it as such.
 
 to the C<double> type in C, and when you need to do any calculations on
 it, you should treat it as such.
 

-

 =head1 GLOBAL FUNCTIONS
 
 These functions can be called anytime, even before initialising the
 =head1 GLOBAL FUNCTIONS
 
 These functions can be called anytime, even before initialising the


@@ -118,13 +157,13 @@ recommended ones.
 
 See the description of C<ev_embed> watchers for more info.
 
 
 See the description of C<ev_embed> watchers for more info.
 

-=item ev_set_allocator (void *(*cb)(void *ptr, long size))
+=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))

 
 

-Sets the allocation function to use (the prototype is similar to the
-realloc C function, the semantics are identical). It is used to allocate
-and free memory (no surprises here). If it returns zero when memory
-needs to be allocated, the library might abort or take some potentially
-destructive action. The default is your system realloc function.
+Sets the allocation function to use (the prototype and semantics are
+identical to the realloc C function). It is used to allocate and free
+memory (no surprises here). If it returns zero when memory needs to be
+allocated, the library might abort or take some potentially destructive
+action. The default is your system realloc function.

 
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,
 
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,


@@ -134,7 +173,7 @@ Example: replace the libev allocator with one that waits a bit and then
 retries: better than mine).
 
    static void *
 retries: better than mine).
 
    static void *

-   persistent_realloc (void *ptr, long size)
+   persistent_realloc (void *ptr, size_t size)

    {
      for (;;)
        {
    {
      for (;;)
        {


@@ -547,6 +586,10 @@ The signal specified in the C<ev_signal> watcher has been received by a thread.
 
 The pid specified in the C<ev_child> watcher has received a status change.
 
 
 The pid specified in the C<ev_child> watcher has received a status change.
 

+=item C<EV_STAT>
+
+The path specified in the C<ev_stat> watcher changed its attributes somehow.
+

 =item C<EV_IDLE>
 
 The C<ev_idle> watcher has determined that you have nothing better to do.
 =item C<EV_IDLE>
 
 The C<ev_idle> watcher has determined that you have nothing better to do.


@@ -563,6 +606,15 @@ many watchers as they want, and all of them will be taken into account
 (for example, a C<ev_prepare> watcher might start an idle watcher to keep
 C<ev_loop> from blocking).
 
 (for example, a C<ev_prepare> watcher might start an idle watcher to keep
 C<ev_loop> from blocking).
 

+=item C<EV_EMBED>
+
+The embedded event loop specified in the C<ev_embed> watcher needs attention.
+
+=item C<EV_FORK>
+
+The event loop has been resumed in the child process after fork (see
+C<ev_fork>).
+

 =item C<EV_ERROR>
 
 An unspecified error has occured, the watcher has been stopped. This might
 =item C<EV_ERROR>
 
 An unspecified error has occured, the watcher has been stopped. This might


@@ -691,7 +743,17 @@ have been omitted....
 =head1 WATCHER TYPES
 
 This section describes each watcher in detail, but will not repeat
 =head1 WATCHER TYPES
 
 This section describes each watcher in detail, but will not repeat

-information given in the last section.
+information given in the last section. Any initialisation/set macros,
+functions and members specific to the watcher type are explained.
+
+Members are additionally marked with either I<[read-only]>, meaning that,
+while the watcher is active, you can look at the member and expect some
+sensible content, but you must not modify it (you can modify it while the
+watcher is stopped to your hearts content), or I<[read-write]>, which
+means you can expect it to have some sensible content while the watcher
+is active, but you can also modify it. Modifying it may not do something
+sensible or take immediate effect (or do anything at all), but libev will
+not crash or malfunction in any way.

 
 
 =head2 C<ev_io> - is this file descriptor readable or writable?
 
 
 =head2 C<ev_io> - is this file descriptor readable or writable?


@@ -744,6 +806,14 @@ Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
 rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
 C<EV_READ | EV_WRITE> to receive the given events.
 
 rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
 C<EV_READ | EV_WRITE> to receive the given events.
 

+=item int fd [read-only]
+
+The file descriptor being watched.
+
+=item int events [read-only]
+
+The events being watched.
+

 =back
 
 Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
 =back
 
 Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well


@@ -816,13 +886,35 @@ If the timer is repeating, either start it if necessary (with the repeat
 value), or reset the running timer to the repeat value.
 
 This sounds a bit complicated, but here is a useful and typical
 value), or reset the running timer to the repeat value.
 
 This sounds a bit complicated, but here is a useful and typical

-example: Imagine you have a tcp connection and you want a so-called idle
-timeout, that is, you want to be called when there have been, say, 60
-seconds of inactivity on the socket. The easiest way to do this is to
-configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
-time you successfully read or write some data. If you go into an idle
-state where you do not expect data to travel on the socket, you can stop
-the timer, and again will automatically restart it if need be.
+example: Imagine you have a tcp connection and you want a so-called
+idle timeout, that is, you want to be called when there have been,
+say, 60 seconds of inactivity on the socket. The easiest way to do
+this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
+C<ev_timer_again> each time you successfully read or write some data. If
+you go into an idle state where you do not expect data to travel on the
+socket, you can stop the timer, and again will automatically restart it if
+need be.
+
+You can also ignore the C<after> value and C<ev_timer_start> altogether
+and only ever use the C<repeat> value:
+
+   ev_timer_init (timer, callback, 0., 5.);
+   ev_timer_again (loop, timer);
+   ...
+   timer->again = 17.;
+   ev_timer_again (loop, timer);
+   ...
+   timer->again = 10.;
+   ev_timer_again (loop, timer);
+
+This is more efficient then stopping/starting the timer eahc time you want
+to modify its timeout value.
+
+=item ev_tstamp repeat [read-write]
+
+The current C<repeat> value. Will be used each time the watcher times out
+or C<ev_timer_again> is called and determines the next timeout (if any),
+which is also when any modifications are taken into account.

 
 =back
 
 
 =back
 


@@ -959,6 +1051,18 @@ when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 

+=item ev_tstamp interval [read-write]
+
+The current interval value. Can be modified any time, but changes only
+take effect when the periodic timer fires or C<ev_periodic_again> is being
+called.
+
+=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
+
+The current reschedule callback, or C<0>, if this functionality is
+switched off. Can be changed any time, but changes only take effect when
+the periodic timer fires or C<ev_periodic_again> is being called.
+

 =back
 
 Example: call a callback every hour, or, more precisely, whenever the
 =back
 
 Example: call a callback every hour, or, more precisely, whenever the


@@ -1018,6 +1122,10 @@ SIG_DFL (regardless of what it was set to before).
 Configures the watcher to trigger on the given signal number (usually one
 of the C<SIGxxx> constants).
 
 Configures the watcher to trigger on the given signal number (usually one
 of the C<SIGxxx> constants).
 

+=item int signum [read-only]
+
+The signal the watcher watches out for.
+

 =back
 
 
 =back
 
 


@@ -1039,6 +1147,19 @@ the status word (use the macros from C<sys/wait.h> and see your systems
 C<waitpid> documentation). The C<rpid> member contains the pid of the
 process causing the status change.
 
 C<waitpid> documentation). The C<rpid> member contains the pid of the
 process causing the status change.
 

+=item int pid [read-only]
+
+The process id this watcher watches out for, or C<0>, meaning any process id.
+
+=item int rpid [read-write]
+
+The process id that detected a status change.
+
+=item int rstatus [read-write]
+
+The process exit/trace status caused by C<rpid> (see your systems
+C<waitpid> and C<sys/wait.h> documentation for details).
+

 =back
 
 Example: try to exit cleanly on SIGINT and SIGTERM.
 =back
 
 Example: try to exit cleanly on SIGINT and SIGTERM.


@@ -1054,6 +1175,104 @@ Example: try to exit cleanly on SIGINT and SIGTERM.
   ev_signal_start (loop, &sigint_cb);
 
 
   ev_signal_start (loop, &sigint_cb);
 
 

+=head2 C<ev_stat> - did the file attributes just change?
+
+This watches a filesystem path for attribute changes. That is, it calls
+C<stat> regularly (or when the OS says it changed) and sees if it changed
+compared to the last time, invoking the callback if it did.
+
+The path does not need to exist: changing from "path exists" to "path does
+not exist" is a status change like any other. The condition "path does
+not exist" is signified by the C<st_nlink> field being zero (which is
+otherwise always forced to be at least one) and all the other fields of
+the stat buffer having unspecified contents.
+
+Since there is no standard to do this, the portable implementation simply
+calls C<stat (2)> regulalry on the path to see if it changed somehow. You
+can specify a recommended polling interval for this case. If you specify
+a polling interval of C<0> (highly recommended!) then a I<suitable,
+unspecified default> value will be used (which you can expect to be around
+five seconds, although this might change dynamically). Libev will also
+impose a minimum interval which is currently around C<0.1>, but thats
+usually overkill.
+
+This watcher type is not meant for massive numbers of stat watchers,
+as even with OS-supported change notifications, this can be
+resource-intensive.
+
+At the time of this writing, no specific OS backends are implemented, but
+if demand increases, at least a kqueue and inotify backend will be added.
+
+=over 4
+
+=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
+
+=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
+
+Configures the watcher to wait for status changes of the given
+C<path>. The C<interval> is a hint on how quickly a change is expected to
+be detected and should normally be specified as C<0> to let libev choose
+a suitable value. The memory pointed to by C<path> must point to the same
+path for as long as the watcher is active.
+
+The callback will be receive C<EV_STAT> when a change was detected,
+relative to the attributes at the time the watcher was started (or the
+last change was detected).
+
+=item ev_stat_stat (ev_stat *)
+
+Updates the stat buffer immediately with new values. If you change the
+watched path in your callback, you could call this fucntion to avoid
+detecting this change (while introducing a race condition). Can also be
+useful simply to find out the new values.
+
+=item ev_statdata attr [read-only]
+
+The most-recently detected attributes of the file. Although the type is of
+C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
+suitable for your system. If the C<st_nlink> member is C<0>, then there
+was some error while C<stat>ing the file.
+
+=item ev_statdata prev [read-only]
+
+The previous attributes of the file. The callback gets invoked whenever
+C<prev> != C<attr>.
+
+=item ev_tstamp interval [read-only]
+
+The specified interval.
+
+=item const char *path [read-only]
+
+The filesystem path that is being watched.
+
+=back
+
+Example: Watch C</etc/passwd> for attribute changes.
+
+  static void
+  passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
+  {
+    /* /etc/passwd changed in some way */
+    if (w->attr.st_nlink)
+      {
+        printf ("passwd current size  %ld\n", (long)w->attr.st_size);
+        printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
+        printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
+      }
+    else
+      /* you shalt not abuse printf for puts */
+      puts ("wow, /etc/passwd is not there, expect problems. "
+            "if this is windows, they already arrived\n");
+  }
+
+  ...
+  ev_stat passwd;
+
+  ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
+  ev_stat_start (loop, &passwd);
+
+

 =head2 C<ev_idle> - when you've got nothing better to do...
 
 Idle watchers trigger events when there are no other events are pending
 =head2 C<ev_idle> - when you've got nothing better to do...
 
 Idle watchers trigger events when there are no other events are pending


@@ -1104,10 +1323,21 @@ Prepare and check watchers are usually (but not always) used in tandem:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 

+You I<must not> call C<ev_loop> or similar functions that enter
+the current event loop from either C<ev_prepare> or C<ev_check>
+watchers. Other loops than the current one are fine, however. The
+rationale behind this is that you do not need to check for recursion in
+those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
+C<ev_check> so if you have one watcher of each kind they will always be
+called in pairs bracketing the blocking call.
+

 Their main purpose is to integrate other event mechanisms into libev and
 their use is somewhat advanced. This could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a
 Their main purpose is to integrate other event mechanisms into libev and
 their use is somewhat advanced. This could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a

-coroutine library and lots more.
+coroutine library and lots more. They are also occasionally useful if
+you cache some data and want to flush it before blocking (for example,
+in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
+watcher).

 
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering C<ev_io> watchers for
 
 This is done by examining in each prepare call which file descriptors need
 to be watched by the other library, registering C<ev_io> watchers for


@@ -1139,7 +1369,60 @@ macros, but using them is utterly, utterly and completely pointless.
 
 =back
 
 
 =back
 

-Example: *TODO*.
+Example: To include a library such as adns, you would add IO watchers
+and a timeout watcher in a prepare handler, as required by libadns, and
+in a check watcher, destroy them and call into libadns. What follows is
+pseudo-code only of course:
+
+  static ev_io iow [nfd];
+  static ev_timer tw;
+
+  static void
+  io_cb (ev_loop *loop, ev_io *w, int revents)
+  {
+    // set the relevant poll flags
+    // could also call adns_processreadable etc. here
+    struct pollfd *fd = (struct pollfd *)w->data;
+    if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+    if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+  }
+
+  // create io watchers for each fd and a timer before blocking
+  static void
+  adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+  {
+    int timeout = 3600000;truct pollfd fds [nfd];
+    // actual code will need to loop here and realloc etc.
+    adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+
+    /* the callback is illegal, but won't be called as we stop during check */
+    ev_timer_init (&tw, 0, timeout * 1e-3);
+    ev_timer_start (loop, &tw);
+
+    // create on ev_io per pollfd
+    for (int i = 0; i < nfd; ++i)
+      {
+        ev_io_init (iow + i, io_cb, fds [i].fd,
+          ((fds [i].events & POLLIN ? EV_READ : 0)
+           | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
+
+        fds [i].revents = 0;
+        iow [i].data = fds + i;
+        ev_io_start (loop, iow + i);
+      }
+  }
+
+  // stop all watchers after blocking
+  static void
+  adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+  {
+    ev_timer_stop (loop, &tw);
+
+    for (int i = 0; i < nfd; ++i)
+      ev_io_stop (loop, iow + i);
+
+    adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+  }

 
 
 =head2 C<ev_embed> - when one backend isn't enough...
 
 
 =head2 C<ev_embed> - when one backend isn't enough...


@@ -1230,6 +1513,31 @@ Make a single, non-blocking sweep over the embedded loop. This works
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
 apropriate way for embedded loops.
 
 similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
 apropriate way for embedded loops.
 

+=item struct ev_loop *loop [read-only]
+
+The embedded event loop.
+
+=back
+
+
+=head2 C<ev_fork> - the audacity to resume the event loop after a fork
+
+Fork watchers are called when a C<fork ()> was detected (usually because
+whoever is a good citizen cared to tell libev about it by calling
+C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
+event loop blocks next and before C<ev_check> watchers are being called,
+and only in the child after the fork. If whoever good citizen calling
+C<ev_default_fork> cheats and calls it in the wrong process, the fork
+handlers will be invoked, too, of course.
+
+=over 4
+
+=item ev_fork_init (ev_signal *, callback)
+
+Initialises and configures the fork watcher - it has no parameters of any
+kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
+believe me.
+

 =back
 
 
 =back
 
 


@@ -1401,6 +1709,10 @@ C<ev_TYPE_again> function.
 
 Invokes C<ev_embed_sweep>.
 
 
 Invokes C<ev_embed_sweep>.
 

+=item w->update ()      C<ev::stat> only
+
+Invokes C<ev_stat_stat>.
+

 =back
 
 =back
 =back
 
 =back


@@ -1423,6 +1735,68 @@ the constructor.
     io.start (fd, ev::READ);
   }
 
     io.start (fd, ev::READ);
   }
 

+
+=head1 MACRO MAGIC
+
+Libev can be compiled with a variety of options, the most fundemantal is
+C<EV_MULTIPLICITY>. This option determines wether (most) functions and
+callbacks have an initial C<struct ev_loop *> argument.
+
+To make it easier to write programs that cope with either variant, the
+following macros are defined:
+
+=over 4
+
+=item C<EV_A>, C<EV_A_>
+
+This provides the loop I<argument> for functions, if one is required ("ev
+loop argument"). The C<EV_A> form is used when this is the sole argument,
+C<EV_A_> is used when other arguments are following. Example:
+
+  ev_unref (EV_A);
+  ev_timer_add (EV_A_ watcher);
+  ev_loop (EV_A_ 0);
+
+It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
+which is often provided by the following macro.
+
+=item C<EV_P>, C<EV_P_>
+
+This provides the loop I<parameter> for functions, if one is required ("ev
+loop parameter"). The C<EV_P> form is used when this is the sole parameter,
+C<EV_P_> is used when other parameters are following. Example:
+
+  // this is how ev_unref is being declared
+  static void ev_unref (EV_P);
+
+  // this is how you can declare your typical callback
+  static void cb (EV_P_ ev_timer *w, int revents)
+
+It declares a parameter C<loop> of type C<struct ev_loop *>, quite
+suitable for use with C<EV_A>.
+
+=item C<EV_DEFAULT>, C<EV_DEFAULT_>
+
+Similar to the other two macros, this gives you the value of the default
+loop, if multiple loops are supported ("ev loop default").
+
+=back
+
+Example: Declare and initialise a check watcher, working regardless of
+wether multiple loops are supported or not.
+
+  static void
+  check_cb (EV_P_ ev_timer *w, int revents)
+  {
+    ev_check_stop (EV_A_ w);
+  }
+
+  ev_check check;
+  ev_check_init (&check, check_cb);
+  ev_check_start (EV_DEFAULT_ &check);
+  ev_loop (EV_DEFAULT_ 0);
+
+

 =head1 EMBEDDING
 
 Libev can (and often is) directly embedded into host
 =head1 EMBEDDING
 
 Libev can (and often is) directly embedded into host


@@ -1638,10 +2012,39 @@ additional independent event loops. Otherwise there will be no support
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
 
 for multiple event loops and there is no first event loop pointer
 argument. Instead, all functions act on the single default loop.
 

-=item EV_PERIODICS
+=item EV_PERIODIC_ENABLE
+
+If undefined or defined to be C<1>, then periodic timers are supported. If
+defined to be C<0>, then they are not. Disabling them saves a few kB of
+code.
+
+=item EV_EMBED_ENABLE
+
+If undefined or defined to be C<1>, then embed watchers are supported. If
+defined to be C<0>, then they are not.
+
+=item EV_STAT_ENABLE
+
+If undefined or defined to be C<1>, then stat watchers are supported. If
+defined to be C<0>, then they are not.
+
+=item EV_FORK_ENABLE

 
 

-If undefined or defined to be C<1>, then periodic timers are supported,
-otherwise not. This saves a few kb of code.
+If undefined or defined to be C<1>, then fork watchers are supported. If
+defined to be C<0>, then they are not.
+
+=item EV_MINIMAL
+
+If you need to shave off some kilobytes of code at the expense of some
+speed, define this symbol to C<1>. Currently only used for gcc to override
+some inlining decisions, saves roughly 30% codesize of amd64.
+
+=item EV_PID_HASHSIZE
+
+C<ev_child> watchers use a small hash table to distribute workload by
+pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
+than enough. If you need to manage thousands of children you might want to
+increase this value.

 
 =item EV_COMMON
 
 
 =item EV_COMMON
 


@@ -1694,6 +2097,34 @@ And a F<ev_cpp.C> implementation file that contains libev proper and is compiled
   #include "ev_cpp.h"
   #include "ev.c"
 
   #include "ev_cpp.h"
   #include "ev.c"
 

+
+=head1 COMPLEXITIES
+
+In this section the complexities of (many of) the algorithms used inside
+libev will be explained. For complexity discussions about backends see the
+documentation for C<ev_default_init>.
+
+=over 4
+
+=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
+
+=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
+
+=item Starting io/check/prepare/idle/signal/child watchers: O(1)
+
+=item Stopping check/prepare/idle watchers: O(1)
+
+=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
+
+=item Finding the next timer per loop iteration: O(1)
+
+=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
+
+=item Activating one watcher: O(1)
+
+=back
+
+

 =head1 AUTHOR
 
 Marc Lehmann <libev@schmorp.de>.
 =head1 AUTHOR
 
 Marc Lehmann <libev@schmorp.de>.