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much better

tags/rel-0.5
Marc Alexander Lehmann 13 years ago
parent
commit
7e9192be63
3 changed files with 187 additions and 42 deletions
  1. +54
    -4
      README
  2. +129
    -35
      ev.c
  3. +4
    -3
      ev.h

+ 54
- 4
README View File

@@ -2,8 +2,58 @@ libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims
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).


+ 129
- 35
ev.c View File

@@ -3,6 +3,7 @@

#include <stdio.h>

#include <assert.h>
#include <errno.h>
#include <sys/time.h>
#include <time.h>
@@ -15,6 +16,7 @@
#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"
@@ -27,6 +29,7 @@ struct ev_watcher_list {
EV_WATCHER_LIST (ev_watcher_list);
};

static ev_tstamp now, diff; /* monotonic clock */
ev_tstamp ev_now;
int ev_method;

@@ -131,11 +134,14 @@ fd_event (int fd, int events)
}
}

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];

@@ -152,15 +158,15 @@ upheap (int 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)
@@ -176,7 +182,7 @@ downheap (int k)
}

static struct ev_signal **signals;
static int signalmax, signalcnt;
static int signalmax;

static void
signals_init (struct ev_signal **base, int count)
@@ -203,6 +209,8 @@ int ev_init (int flags)
#endif

ev_now = ev_time ();
now = get_clock ();
diff = ev_now - now;

#if HAVE_EPOLL
if (epoll_init (flags))
@@ -252,32 +260,77 @@ call_pending ()
}

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;
@@ -288,25 +341,38 @@ int ev_loop (int flags)
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);
@@ -393,14 +459,22 @@ evtimer_start (struct ev_timer *w)
/* 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
@@ -409,10 +483,21 @@ evtimer_stop (struct ev_timer *w)
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);
@@ -451,7 +536,9 @@ sin_cb (struct ev_io *w, int revents)
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)
@@ -464,18 +551,25 @@ 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);



+ 4
- 3
ev.h View File

@@ -26,9 +26,9 @@ struct ev_timer
{
EV_WATCHER_LIST (ev_timer);

ev_tstamp at; /* ro */
ev_tstamp at; /* private */
ev_tstamp repeat; /* rw */
unsigned char is_abs; /* rw */
unsigned char is_abs; /* ro */
};

struct ev_io
@@ -61,11 +61,12 @@ ev_tstamp ev_time (void);

#define EVLOOP_NONBLOCK 1 /* do not block/wait */
#define EVLOOP_ONESHOT 2 /* block *once* only */
int ev_loop (int flags);
void ev_loop (int flags);
extern int ev_loop_done; /* set to 1 to break out of event loop */

/* these may evaluate ev multiple times, and the other arguments at most once */
#define evw_init(ev,cb_,data_) do { (ev)->active = 0; (ev)->cb = (cb_); (ev)->data = (void *)data_; } while (0)

#define evio_set(ev,fd_,events_) do { (ev)->fd = (fd_); (ev)->events = (events_); } while (0)
#define evtimer_set_rel(ev,after_,repeat_) do { (ev)->at = (after_); (ev)->repeat = (repeat_); (ev)->is_abs = 0; } while (0)
#define evtimer_set_abs(ev,at_,repeat_) do { (ev)->at = (at_); (ev)->repeat = (repeat_); (ev)->is_abs = 1; } while (0)


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