Allocate connections structs lazily.

Keep memory use down when there are few simultaneous connections.
Allocate connection structs on demand, but save them in a free list
and reuse them for faster operation under load. Also remove the hard
limit on number of simultaneous connections.

beanstalkd.c

@@ -425,7 +425,6 @@ main(int argc, char **argv)
 
  drop_root();
  prot_init();
- conn_init();
  daemonize();
  event_init();
  set_sig_handlers();

conn.c

@@ -8,10 +8,8 @@
 #include "util.h"
 #include "prot.h"
 
-static struct conn pool[MAX_CONNECTIONS];
-
 /* linked list of free connections. See struct conn's next field in conn.h */
-static conn pool_front, pool_rear;
+static conn pool_front = NULL, pool_rear = NULL;
 
 static int
 pool_conn_p()
@@ -24,7 +22,7 @@ conn_alloc()
 {
  conn c;
 
- if (!pool_conn_p()) return NULL;
+ if (!pool_conn_p()) return malloc(sizeof(struct conn));
 
  /* remove it from the list */
  c = pool_front;
@@ -47,22 +45,13 @@ conn_free(conn c)
  pool_rear = c;
 }
 
-void
-conn_init()
-{
- int i;
-
- pool_front = pool_rear = NULL;
- for (i = 0; i < MAX_CONNECTIONS; i++) conn_free(&pool[i]);
-}
-
 conn
 make_conn(int fd, char start_state)
 {
  conn c;
 
  c = conn_alloc();
- if (!c) return NULL;
+ if (!c) return warn("OOM"), NULL;
 
  c->fd = fd;
  c->state = start_state;

conn.h

@@ -6,9 +6,6 @@
 #include "event.h"
 #include "job.h"
 
-/* We will stop accepting new connections at 8 simultaneous Ki-connections. */
-#define MAX_CONNECTIONS (8 * 1024)
-
 #define STATE_WANTCOMMAND 0
 #define STATE_WANTDATA 1
 #define STATE_SENDJOB 2