Limit the maximum number of events on each socket to 65535

This lets us use less RAM for the evmap_io structure, which in turn
can let us have fewer cache misses for evmap operations.

diff --git a/evmap.c b/evmap.c
index 9e32cf065e31b4aa2088e67216c55790eaf91ddc..b11ec3c91b5005b928d4342bf418b331827419ae 100644 (file)
--- a/evmap.c
+++ b/evmap.c
@@ -56,8 +56,8 @@
   */
 struct evmap_io {
        struct event_list events;
-       unsigned int nread;
-       unsigned int nwrite;
+       ev_uint16_t nread;
+       ev_uint16_t nwrite;
 };
 
 /* An entry for an evmap_signal list: notes all the events that want to know
@@ -295,6 +295,11 @@ evmap_io_add(struct event_base *base, evutil_socket_t fd, struct event *ev)
                if (++nwrite == 1)
                        res |= EV_WRITE;
        }
+       if (EVUTIL_UNLIKELY(nread > 0xffff || nwrite > 0xffff)) {
+               event_warnx("Too many events reading or writing on fd %d",
+                   (int)fd);
+               return -1;
+       }
 
        if (res) {
                void *extra = ((char*)ctx) + sizeof(struct evmap_io);
@@ -307,8 +312,8 @@ evmap_io_add(struct event_base *base, evutil_socket_t fd, struct event *ev)
                retval = 1;
        }
 
-       ctx->nread = nread;
-       ctx->nwrite = nwrite;
+       ctx->nread = (ev_uint16_t) nread;
+       ctx->nwrite = (ev_uint16_t) nwrite;
        TAILQ_INSERT_TAIL(&ctx->events, ev, ev_io_next);
 
        return (retval);