performance improvements of select handler by Nick Mathewson; I added

better recovery when memory allocation fails; something that needs to be
done for the poll improvements, too.

svn:r166

diff --git a/select.c b/select.c
index b70a780c79ac7815f1cfbd9f1098f22b4d91e4fd..00909b79051e53bbdfb40de143ad4ace295a72cc 100644 (file)
--- a/select.c
+++ b/select.c
@@ -44,6 +44,9 @@
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
+#ifdef CHECK_INVARIANTS
+#include <assert.h>
+#endif
 
 #include "event.h"
 #include "event-internal.h"
@@ -59,8 +62,12 @@ extern volatile sig_atomic_t evsignal_caught;
 struct selectop {
        int event_fds;          /* Highest fd in fd set */
        int event_fdsz;
-       fd_set *event_readset;
-       fd_set *event_writeset;
+       fd_set *event_readset_in;
+       fd_set *event_writeset_in;
+       fd_set *event_readset_out;
+       fd_set *event_writeset_out;
+       struct event **event_r_by_fd;
+       struct event **event_w_by_fd;
        sigset_t evsigmask;
 };
 
@@ -79,6 +86,8 @@ const struct eventop selectops = {
        select_dispatch
 };
 
+static int select_resize(struct selectop *sop, int fdsz);
+
 void *
 select_init(void)
 {
@@ -91,11 +100,40 @@ select_init(void)
        if (!(sop = calloc(1, sizeof(struct selectop))))
                return (NULL);
 
+       select_resize(sop, howmany(32 + 1, NFDBITS)*sizeof(fd_mask));
+
        evsignal_init(&sop->evsigmask);
 
        return (sop);
 }
 
+#ifdef CHECK_INVARIANTS
+static void
+check_selectop(struct selectop *sop)
+{
+       int i;
+       for (i=0;i<=sop->event_fds;++i) {
+               if (FD_ISSET(i, sop->event_readset_in)) {
+                       assert(sop->event_r_by_fd[i]);
+                       assert(sop->event_r_by_fd[i]->ev_events & EV_READ);
+                       assert(sop->event_r_by_fd[i]->ev_fd == i);
+               } else {
+                       assert(! sop->event_r_by_fd[i]);
+               }
+               if (FD_ISSET(i, sop->event_writeset_in)) {
+                       assert(sop->event_w_by_fd[i]);
+                       assert(sop->event_w_by_fd[i]->ev_events & EV_WRITE);
+                       assert(sop->event_w_by_fd[i]->ev_fd == i);
+               } else {
+                       assert(! sop->event_w_by_fd[i]);
+               }
+       }
+
+}
+#else
+#define check_selectop(sop)
+#endif
+
 /*
  * Called with the highest fd that we know about.  If it is 0, completely
  * recalculate everything.
@@ -105,41 +143,8 @@ int
 select_recalc(struct event_base *base, void *arg, int max)
 {
        struct selectop *sop = arg;
-       fd_set *readset, *writeset;
-       struct event *ev;
-       int fdsz;
-
-       if (sop->event_fds < max)
-               sop->event_fds = max;
 
-       if (!sop->event_fds) {
-               TAILQ_FOREACH(ev, &base->eventqueue, ev_next)
-                       if (ev->ev_fd > sop->event_fds)
-                               sop->event_fds = ev->ev_fd;
-       }
-
-       fdsz = howmany(sop->event_fds + 1, NFDBITS) * sizeof(fd_mask);
-       if (fdsz > sop->event_fdsz) {
-               if ((readset = realloc(sop->event_readset, fdsz)) == NULL) {
-                       event_warn("malloc");
-                       return (-1);
-               }
-
-               if ((writeset = realloc(sop->event_writeset, fdsz)) == NULL) {
-                       event_warn("malloc");
-                       free(readset);
-                       return (-1);
-               }
-
-               memset((char *)readset + sop->event_fdsz, 0,
-                   fdsz - sop->event_fdsz);
-               memset((char *)writeset + sop->event_fdsz, 0,
-                   fdsz - sop->event_fdsz);
-
-               sop->event_readset = readset;
-               sop->event_writeset = writeset;
-               sop->event_fdsz = fdsz;
-       }
+       check_selectop(sop);
 
        return (evsignal_recalc(&sop->evsigmask));
 }
@@ -147,26 +152,23 @@ select_recalc(struct event_base *base, void *arg, int max)
 int
 select_dispatch(struct event_base *base, void *arg, struct timeval *tv)
 {
-       int maxfd, res;
-       struct event *ev, *next;
+       int res, i;
        struct selectop *sop = arg;
 
-       memset(sop->event_readset, 0, sop->event_fdsz);
-       memset(sop->event_writeset, 0, sop->event_fdsz);
+       check_selectop(sop);
 
-       TAILQ_FOREACH(ev, &base->eventqueue, ev_next) {
-               if (ev->ev_events & EV_WRITE)
-                       FD_SET(ev->ev_fd, sop->event_writeset);
-               if (ev->ev_events & EV_READ)
-                       FD_SET(ev->ev_fd, sop->event_readset);
-       }
+       memcpy(sop->event_readset_out, sop->event_readset_in,
+              sop->event_fdsz);
+       memcpy(sop->event_writeset_out, sop->event_writeset_in,
+              sop->event_fdsz);
 
        if (evsignal_deliver(&sop->evsigmask) == -1)
                return (-1);
 
-       res = select(sop->event_fds + 1, sop->event_readset, 
-           sop->event_writeset, NULL, tv);
+       res = select(sop->event_fds + 1, sop->event_readset_out,
+           sop->event_writeset_out, NULL, tv);
 
+       check_selectop(sop);
        if (evsignal_recalc(&sop->evsigmask) == -1)
                return (-1);
 
@@ -183,32 +185,94 @@ select_dispatch(struct event_base *base, void *arg, struct timeval *tv)
 
        event_debug(("%s: select reports %d", __func__, res));
 
-       maxfd = 0;
-       for (ev = TAILQ_FIRST(&base->eventqueue); ev != NULL; ev = next) {
-               next = TAILQ_NEXT(ev, ev_next);
-
+       check_selectop(sop);
+       for (i = 0; i <= sop->event_fds; ++i) {
+               struct event *r_ev = NULL, *w_ev = NULL;
                res = 0;
-               if (FD_ISSET(ev->ev_fd, sop->event_readset))
+               if (FD_ISSET(i, sop->event_readset_out)) {
+                       r_ev = sop->event_r_by_fd[i];
                        res |= EV_READ;
-               if (FD_ISSET(ev->ev_fd, sop->event_writeset))
+               }
+               if (FD_ISSET(i, sop->event_writeset_out)) {
+                       w_ev = sop->event_w_by_fd[i];
                        res |= EV_WRITE;
-               res &= ev->ev_events;
-
-               if (res) {
-                       if (!(ev->ev_events & EV_PERSIST))
-                               event_del(ev);
-                       else if (ev->ev_fd > maxfd)
-                               maxfd = ev->ev_fd;
-                       event_active(ev, res, 1);
-               } else if (ev->ev_fd > maxfd)
-                       maxfd = ev->ev_fd;
+               }
+               if (r_ev && (res & r_ev->ev_events)) {
+                       if (!(r_ev->ev_events & EV_PERSIST))
+                               event_del(r_ev);
+                       event_active(r_ev, res & r_ev->ev_events, 1);
+               }
+               if (w_ev && w_ev != r_ev && (res & w_ev->ev_events)) {
+                       if (!(w_ev->ev_events & EV_PERSIST))
+                               event_del(w_ev);
+                       event_active(w_ev, res & w_ev->ev_events, 1);
+               }
        }
+       check_selectop(sop);
 
-       sop->event_fds = maxfd;
+       return (0);
+}
+
+
+static int
+select_resize(struct selectop *sop, int fdsz)
+{
+       int n_events, n_events_old;
+
+       fd_set *readset_in = NULL;
+       fd_set *writeset_in = NULL;
+       fd_set *readset_out = NULL;
+       fd_set *writeset_out = NULL;
+       struct event **r_by_fd = NULL;
+       struct event **w_by_fd = NULL;
+
+       n_events = (fdsz/sizeof(fd_mask)) * NFDBITS;
+       n_events_old = (sop->event_fdsz/sizeof(fd_mask)) * NFDBITS;
+
+       if (sop->event_readset_in)
+               check_selectop(sop);
+
+       if ((readset_in = realloc(sop->event_readset_in, fdsz)) == NULL)
+               goto error;
+       sop->event_readset_in = readset_in;
+       if ((readset_out = realloc(sop->event_readset_out, fdsz)) == NULL)
+               goto error;
+       sop->event_readset_out = readset_out;
+       if ((writeset_in = realloc(sop->event_writeset_in, fdsz)) == NULL)
+               goto error;
+       sop->event_writeset_in = writeset_in;
+       if ((writeset_out = realloc(sop->event_writeset_out, fdsz)) == NULL)
+               goto error;
+       sop->event_writeset_out = writeset_out;
+       if ((r_by_fd = realloc(sop->event_r_by_fd,
+                n_events*sizeof(struct event*))) == NULL)
+               goto error;
+       sop->event_r_by_fd = r_by_fd;
+       if ((w_by_fd = realloc(sop->event_w_by_fd,
+                n_events * sizeof(struct event*))) == NULL)
+               goto error;
+       sop->event_w_by_fd = w_by_fd;
+
+       memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
+           fdsz - sop->event_fdsz);
+       memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
+           fdsz - sop->event_fdsz);
+       memset(sop->event_r_by_fd + n_events_old, 0,
+           (n_events-n_events_old) * sizeof(struct event*));
+       memset(sop->event_w_by_fd + n_events_old, 0,
+           (n_events-n_events_old) * sizeof(struct event*));
+
+       sop->event_fdsz = fdsz;
+       check_selectop(sop);
 
        return (0);
+
+ error:
+       event_warn("malloc");
+       return (-1);
 }
 
+
 int
 select_add(void *arg, struct event *ev)
 {
@@ -217,12 +281,40 @@ select_add(void *arg, struct event *ev)
        if (ev->ev_events & EV_SIGNAL)
                return (evsignal_add(&sop->evsigmask, ev));
 
-       /* 
+       check_selectop(sop);
+       /*
         * Keep track of the highest fd, so that we can calculate the size
         * of the fd_sets for select(2)
         */
-       if (sop->event_fds < ev->ev_fd)
+       if (sop->event_fds < ev->ev_fd) {
+               int fdsz = sop->event_fdsz;
+
+               if (fdsz < sizeof(fd_mask))
+                       fdsz = sizeof(fd_mask);
+
+               while (fdsz <
+                   (howmany(ev->ev_fd + 1, NFDBITS) * sizeof(fd_mask)))
+                       fdsz *= 2;
+
+               if (fdsz != sop->event_fdsz) {
+                       if (select_resize(sop, fdsz)) {
+                               check_selectop(sop);
+                               return (-1);
+                       }
+               }
+
                sop->event_fds = ev->ev_fd;
+       }
+
+       if (ev->ev_events & EV_READ) {
+               FD_SET(ev->ev_fd, sop->event_readset_in);
+               sop->event_r_by_fd[ev->ev_fd] = ev;
+       }
+       if (ev->ev_events & EV_WRITE) {
+               FD_SET(ev->ev_fd, sop->event_writeset_in);
+               sop->event_w_by_fd[ev->ev_fd] = ev;
+       }
+       check_selectop(sop);
 
        return (0);
 }
@@ -236,8 +328,25 @@ select_del(void *arg, struct event *ev)
 {
        struct selectop *sop = arg;
 
-       if (!(ev->ev_events & EV_SIGNAL))
+       check_selectop(sop);
+       if (ev->ev_events & EV_SIGNAL)
+               return (evsignal_del(&sop->evsigmask, ev));
+
+       if (sop->event_fds < ev->ev_fd) {
+               check_selectop(sop);
                return (0);
+       }
+
+       if (ev->ev_events & EV_READ) {
+               FD_CLR(ev->ev_fd, sop->event_readset_in);
+               sop->event_r_by_fd[ev->ev_fd] = NULL;
+       }
 
-       return (evsignal_del(&sop->evsigmask, ev));
+       if (ev->ev_events & EV_WRITE) {
+               FD_CLR(ev->ev_fd, sop->event_writeset_in);
+               sop->event_w_by_fd[ev->ev_fd] = NULL;
+       }
+
+       check_selectop(sop);
+       return (0);
 }