problem: zmq_poll is slow because FD is being created on every call

making the creation of FD only when thread safe sockets are in used
within the zmq_poller which improve the zmq_poll performance.

src/socket_poller.cpp

@@ -33,6 +33,7 @@
 
 zmq::socket_poller_t::socket_poller_t () :
     tag (0xCAFEBABE),
+    signaler (NULL),
     need_rebuild (true),
     use_signaler (false),
     poll_size(0)
@@ -62,10 +63,15 @@ zmq::socket_poller_t::~socket_poller_t ()
             size_t thread_safe_size = sizeof(int);
 
             if (it->socket->getsockopt (ZMQ_THREAD_SAFE, &thread_safe, &thread_safe_size) == 0 && thread_safe)
-                it->socket->remove_signaler (&signaler);
+                it->socket->remove_signaler (signaler);
         }
     }
 
+    if (signaler != NULL) {
+        delete signaler;
+        signaler = NULL;
+    }
+
 #if defined ZMQ_POLL_BASED_ON_POLL
     if (pollfds) {
         free (pollfds);
@@ -95,7 +101,10 @@ int zmq::socket_poller_t::add (socket_base_t *socket_, void* user_data_, short e
         return -1;
 
     if (thread_safe) {
-        if (socket_->add_signaler (&signaler) == -1)
+        if (signaler == NULL)
+            signaler = new signaler_t ();
+
+        if (socket_->add_signaler (signaler) == -1)
            return -1;
     }
 
@@ -193,7 +202,7 @@ int zmq::socket_poller_t::remove (socket_base_t *socket_)
     size_t thread_safe_size = sizeof(int);
 
     if (socket_->getsockopt (ZMQ_THREAD_SAFE, &thread_safe, &thread_safe_size) == 0 && thread_safe)
-        socket_->remove_signaler (&signaler);
+        socket_->remove_signaler (signaler);
 
     return 0;
 }
@@ -264,7 +273,7 @@ int zmq::socket_poller_t::rebuild ()
 
     if (use_signaler) {
         item_nbr = 1;
-        pollfds[0].fd = signaler.get_fd();
+        pollfds[0].fd = signaler->get_fd();
         pollfds[0].events = POLLIN;
     }
 
@@ -323,7 +332,7 @@ int zmq::socket_poller_t::rebuild ()
 
             if (thread_safe && it->events) {
                 use_signaler = true;
-                FD_SET (signaler.get_fd (), &pollset_in);
+                FD_SET (signaler->get_fd (), &pollset_in);
                 poll_size = 1;
                 break;
             }
@@ -436,7 +445,7 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
 
         //  Receive the signal from pollfd
         if (use_signaler && pollfds[0].revents & POLLIN)
-            signaler.recv ();
+            signaler->recv ();
 
         //  Check for the events.
         int found = 0;
@@ -596,8 +605,8 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
             break;
         }
 
-        if (use_signaler && FD_ISSET (signaler.get_fd (), &inset))
-            signaler.recv ();
+        if (use_signaler && FD_ISSET (signaler->get_fd (), &inset))
+            signaler->recv ();
 
         //  Check for the events.
         int found = 0;

src/socket_poller.hpp

@@ -87,7 +87,7 @@ namespace zmq
         uint32_t tag;
 
         //  Signaler used for thread safe sockets polling
-        signaler_t signaler;
+        signaler_t* signaler;
 
         typedef struct item_t {
             socket_base_t *socket;