to be faster and more correct, and also more featureful. Examples:
- multiple watchers can wait for the same event without deregistering others.
-- fork() is supported and can be handled.
-- timers are handled as a priority queue (faster)
-- watchers use less memory (faster)
-- less calls to epoll_ctl (faster)
+ (registering two read events on fd 10 and unregistering one will not
+ break the other)
+
+- fork() is supported and can be handled
+ (there is no way to recover from a fork when libevent is active)
+
+- timers are handled as a priority queue
+ (libevent uses a less efficient red-black tree)
+
+- supports absolute (wallclock-based) timers in addition to relative ones,
+ i.e. can schedule timers to occur after n seconds, or at a specific time.
+
+- timers can be repeating (both absolute and relative ones)
+
+- detects time jumps and adjusts timers
+ (works for both forward and backward time jumps and also for absolute timers)
+
+- can correctly remove timers while executing callbacks
+ (libevent doesn't handle this reliably and can crash)
+
+- less calls to epoll_ctl
+ (stopping and starting an io watcher between two loop iterations will now
+ result in spuriois epoll_ctl calls)
+
+- usually less calls to gettimeofday and clock_gettime
+ (libevent calls it on every timer event change, libev twice per iteration)
+
+- watchers use less memory
+ (libevent on amd64: 152 bytes, libev: <= 56 bytes)
+
+- library uses less memory
+ (libevent allocates large data structures wether used or not, libev
+ scales all its data structures dynamically)
+
+- no hardcoded arbitrary limits
+ (libevent contains an off-by-one bug and sometimes hardcodes a limit of
+ 32000 fds)
+
+- libev separates timer, signal and io watchers from each other
+ (libevent combines them, but with libev you can combine them yourself
+ by reusing the same callback and still save memory)
+
+- simpler design, backends are potentially much simpler
+ (in libevent, backends have to deal with watchers, thus the problems)
+ (epoll backend in libevent: 366 lines, libev: 89 lines, and more features)
+
+whats missing?
+
+- evdns, evhttp, bufferevent are missing, libev is only an even library at
+ the moment.
+
+- no priority support at the moment.
+
+- kqueue, poll (libev currently implements epoll and select).
#include <stdio.h>
+#include <assert.h>
#include <errno.h>
#include <sys/time.h>
#include <time.h>
#define HAVE_REALTIME 1
#define HAVE_SELECT 0
+#define MIN_TIMEJUMP 1. /* minimum timejump that gets detected (if monotonic clock available) */
#define MAX_BLOCKTIME 60.
#include "ev.h"
EV_WATCHER_LIST (ev_watcher_list);
};
+static ev_tstamp now, diff; /* monotonic clock */
ev_tstamp ev_now;
int ev_method;
}
}
-static struct ev_timer **timers;
-static int timermax, timercnt;
+static struct ev_timer **atimers;
+static int atimermax, atimercnt;
+
+static struct ev_timer **rtimers;
+static int rtimermax, rtimercnt;
static void
-upheap (int k)
+upheap (struct ev_timer **timers, int k)
{
struct ev_timer *w = timers [k];
}
static void
-downheap (int k)
+downheap (struct ev_timer **timers, int N, int k)
{
struct ev_timer *w = timers [k];
- while (k < (timercnt >> 1))
+ while (k < (N >> 1))
{
int j = k << 1;
- if (j + 1 < timercnt && timers [j]->at > timers [j + 1]->at)
+ if (j + 1 < N && timers [j]->at > timers [j + 1]->at)
++j;
if (w->at <= timers [j]->at)
}
static struct ev_signal **signals;
-static int signalmax, signalcnt;
+static int signalmax;
static void
signals_init (struct ev_signal **base, int count)
#endif
ev_now = ev_time ();
+ now = get_clock ();
+ diff = ev_now - now;
#if HAVE_EPOLL
if (epoll_init (flags))
}
static void
-timer_reify (void)
+timers_reify (struct ev_timer **timers, int timercnt, ev_tstamp now)
{
- while (timercnt && timers [0]->at <= ev_now)
+ while (timercnt && timers [0]->at <= now)
{
struct ev_timer *w = timers [0];
- /* first reschedule timer */
+ /* first reschedule or stop timer */
if (w->repeat)
{
if (w->is_abs)
- w->at += ceil ((ev_now - w->at) / w->repeat + 1.) * w->repeat;
+ w->at += floor ((now - w->at) / w->repeat + 1.) * w->repeat;
else
- w->at = ev_now + w->repeat;
+ w->at = now + w->repeat;
+
+ assert (w->at > now);
- downheap (0);
+ downheap (timers, timercnt, 0);
}
else
- evtimer_stop (w); /* nonrepeating: stop timer */
+ {
+ evtimer_stop (w); /* nonrepeating: stop timer */
+ --timercnt; /* maybe pass by reference instead? */
+ }
event ((struct ev_watcher *)w, EV_TIMEOUT);
}
}
+static void
+time_update ()
+{
+ int i;
+ ev_now = ev_time ();
+
+ if (have_monotonic)
+ {
+ ev_tstamp odiff = diff;
+
+ /* detecting time jumps is much more difficult */
+ for (i = 2; --i; ) /* loop a few times, before making important decisions */
+ {
+ now = get_clock ();
+ diff = ev_now - now;
+
+ if (fabs (odiff - diff) < MIN_TIMEJUMP)
+ return; /* all is well */
+
+ ev_now = ev_time ();
+ }
+
+ /* time jump detected, reschedule atimers */
+ for (i = 0; i < atimercnt; ++i)
+ {
+ struct ev_timer *w = atimers [i];
+ w->at += ceil ((ev_now - w->at) / w->repeat + 1.) * w->repeat;
+ }
+ }
+ else
+ {
+ if (now > ev_now || now < ev_now - MAX_BLOCKTIME - MIN_TIMEJUMP)
+ /* time jump detected, adjust rtimers */
+ for (i = 0; i < rtimercnt; ++i)
+ rtimers [i]->at += ev_now - now;
+
+ now = ev_now;
+ }
+}
+
int ev_loop_done;
-int ev_loop (int flags)
+void ev_loop (int flags)
{
double block;
ev_loop_done = flags & EVLOOP_ONESHOT;
method_reify (); fdchangecnt = 0;
/* calculate blocking time */
- ev_now = ev_time ();
-
if (flags & EVLOOP_NONBLOCK)
block = 0.;
- else if (!timercnt)
- block = MAX_BLOCKTIME;
else
{
- block = timers [0]->at - ev_now + method_fudge;
+ block = MAX_BLOCKTIME;
+
+ if (rtimercnt)
+ {
+ ev_tstamp to = rtimers [0]->at - get_clock () + method_fudge;
+ if (block > to) block = to;
+ }
+
+ if (atimercnt)
+ {
+ ev_tstamp to = atimers [0]->at - ev_time () + method_fudge;
+ if (block > to) block = to;
+ }
+
if (block < 0.) block = 0.;
- else if (block > MAX_BLOCKTIME) block = MAX_BLOCKTIME;
}
method_poll (block);
+ /* update ev_now, do magic */
+ time_update ();
+
/* put pending timers into pendign queue and reschedule them */
- timer_reify ();
+ /* absolute timers first */
+ timers_reify (atimers, atimercnt, ev_now);
+ /* relative timers second */
+ timers_reify (rtimers, rtimercnt, now);
- ev_now = ev_time ();
call_pending ();
}
while (!ev_loop_done);
/* this formula differs from the one in timer_reify becuse we do not round up */
if (w->repeat)
w->at += ceil ((ev_now - w->at) / w->repeat) * w->repeat;
+
+ ev_start ((struct ev_watcher *)w, ++atimercnt);
+ array_needsize (atimers, atimermax, atimercnt, );
+ atimers [atimercnt - 1] = w;
+ upheap (atimers, atimercnt - 1);
}
else
- w->at += ev_now;
+ {
+ w->at += now;
+
+ ev_start ((struct ev_watcher *)w, ++rtimercnt);
+ array_needsize (rtimers, rtimermax, rtimercnt, );
+ rtimers [rtimercnt - 1] = w;
+ upheap (rtimers, rtimercnt - 1);
+ }
- ev_start ((struct ev_watcher *)w, ++timercnt);
- array_needsize (timers, timermax, timercnt, );
- timers [timercnt - 1] = w;
- upheap (timercnt - 1);
}
void
if (!ev_is_active (w))
return;
- if (w->active < timercnt--)
+ if (w->is_abs)
{
- timers [w->active - 1] = timers [timercnt];
- downheap (w->active - 1);
+ if (w->active < atimercnt--)
+ {
+ atimers [w->active - 1] = atimers [atimercnt];
+ downheap (atimers, atimercnt, w->active - 1);
+ }
+ }
+ else
+ {
+ if (w->active < rtimercnt--)
+ {
+ rtimers [w->active - 1] = rtimers [rtimercnt];
+ downheap (rtimers, rtimercnt, w->active - 1);
+ }
}
ev_stop ((struct ev_watcher *)w);
static void
ocb (struct ev_timer *w, int revents)
{
- fprintf (stderr, "timer %f,%f (%x) (%f) d%p\n", w->at, w->repeat, revents, w->at - ev_time (), w->data);
+ //fprintf (stderr, "timer %f,%f (%x) (%f) d%p\n", w->at, w->repeat, revents, w->at - ev_time (), w->data);
+ evtimer_stop (w);
+ evtimer_start (w);
}
int main (void)
evio_set (&sin, 0, EV_READ);
evio_start (&sin);
- struct ev_timer t[1000];
+ struct ev_timer t[10000];
+#if 1
int i;
- for (i = 0; i < 1000; ++i)
+ for (i = 0; i < 10000; ++i)
{
struct ev_timer *w = t + i;
evw_init (w, ocb, i);
- evtimer_set_rel (w, drand48 (), 0);
+ evtimer_set_abs (w, drand48 (), 0.99775533);
evtimer_start (w);
if (drand48 () < 0.5)
evtimer_stop (w);
}
+#endif
+
+ struct ev_timer t1;
+ evw_init (&t1, ocb, 0);
+ evtimer_set_abs (&t1, 5, 10);
+ evtimer_start (&t1);
ev_loop (0);
projects / software / libev.git / commitdiff