Add event_config_set_num_cpus_hint for tuning thread pools, etc.

event-internal.h

@@ -285,6 +285,7 @@ struct event_config_entry {
 struct event_config {
 	TAILQ_HEAD(event_configq, event_config_entry) entries;
 
+	int n_cpus_hint;
 	enum event_method_feature require_features;
 	enum event_base_config_flag flags;
 };

event.c

@@ -615,19 +615,19 @@ event_base_new_with_config(const struct event_config *cfg)
 
 #ifdef WIN32
 	if (cfg && (cfg->flags & EVENT_BASE_FLAG_STARTUP_IOCP))
-		event_base_start_iocp(base);
+		event_base_start_iocp(base, cfg->n_cpus_hint);
 #endif
 
 	return (base);
 }
 
 int
-event_base_start_iocp(struct event_base *base)
+event_base_start_iocp(struct event_base *base, int n_cpus)
 {
 #ifdef WIN32
 	if (base->iocp)
 		return 0;
-	base->iocp = event_iocp_port_launch();
+	base->iocp = event_iocp_port_launch(n_cpus);
 	if (!base->iocp) {
 		event_warnx("%s: Couldn't launch IOCP", __func__);
 		return -1;
@@ -918,6 +918,15 @@ event_config_require_features(struct event_config *cfg,
 	return (0);
 }
 
+int
+event_config_set_num_cpus_hint(struct event_config *cfg, int cpus)
+{
+	if (!cfg)
+		return (-1);
+	cfg->n_cpus_hint = cpus;
+	return (0);
+}
+
 int
 event_priority_init(int npriorities)
 {

event_iocp.c

@@ -162,8 +162,10 @@ event_get_win32_extension_fns(void)
 	return &the_extension_fns;
 }
 
+#define N_CPUS_DEFAULT 2
+
 struct event_iocp_port *
-event_iocp_port_launch(void)
+event_iocp_port_launch(int n_cpus)
 {
 	struct event_iocp_port *port;
 	int i;
@@ -173,12 +175,16 @@ event_iocp_port_launch(void)
 
 	if (!(port = mm_calloc(1, sizeof(struct event_iocp_port))))
 		return NULL;
-	port->n_threads = 2;
+
+	if (n_cpus <= 0)
+		n_cpus = N_CPUS_DEFAULT;
+	port->n_threads = n_cpus * 2;
 	port->threads = calloc(port->n_threads, sizeof(HANDLE));
 	if (!port->threads)
 		goto err;
 
-	port->port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, port->n_threads);
+	port->port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0,
+			n_cpus);
 	port->ms = -1;
 	if (!port->port)
 		goto err;

include/event2/event.h

@@ -226,6 +226,16 @@ int event_config_require_features(struct event_config *cfg, int feature);
  * will be initialized, and how they'll work. */
 int event_config_set_flag(struct event_config *cfg, int flag);
 
+/**
+ * Records a hint for the number of CPUs in the system. This is used for
+ * tuning thread pools, etc, for optimal performance.
+ *
+ * @param cfg the event configuration object
+ * @param cpus the number of cpus
+ * @return 0 on success, -1 on failure.
+ */
+int event_config_set_num_cpus_hint(struct event_config *cfg, int cpus);
+
 /**
   Initialize the event API.
 

iocp-internal.h

@@ -155,7 +155,7 @@ void evbuffer_commit_write(struct evbuffer *, ev_ssize_t);
 
     This interface is unstable, and will change.
  */
-struct event_iocp_port *event_iocp_port_launch(void);
+struct event_iocp_port *event_iocp_port_launch(int n_cpus);
 
 /** Associate a file descriptor with an iocp, such that overlapped IO on the
     fd will happen on one of the iocp's worker threads.
@@ -181,7 +181,7 @@ struct event_base;
 struct event_iocp_port *event_base_get_iocp(struct event_base *base);
 
 /* FIXME document. */
-int event_base_start_iocp(struct event_base *base);
+int event_base_start_iocp(struct event_base *base, int n_cpus);
 void event_base_stop_iocp(struct event_base *base);
 
 /* FIXME document. */

test/bench_http.c

@@ -133,7 +133,7 @@ main(int argc, char **argv)
 		case 'i':
 			use_iocp = 1;
 			evthread_use_windows_threads();
-			event_base_start_iocp(base);
+			event_base_start_iocp(base, 0);
 			break;
 #endif
 		default:

test/regress_iocp.c

@@ -170,7 +170,7 @@ test_iocp_port(void *ptr)
 	event_overlapped_init(&o1.eo, dummy_cb);
 	event_overlapped_init(&o2.eo, dummy_cb);
 
-	port = event_iocp_port_launch();
+	port = event_iocp_port_launch(0);
 	tt_assert(port);
 
 	tt_assert(!event_iocp_activate_overlapped(port, &o1.eo, 10, 100));
@@ -255,7 +255,7 @@ test_iocp_evbuffer(void *ptr)
 	evbuffer_enable_locking(rbuf, NULL);
 	evbuffer_enable_locking(wbuf, NULL);
 
-	port = event_iocp_port_launch();
+	port = event_iocp_port_launch(0);
 	tt_assert(port);
 	tt_assert(rbuf);
 	tt_assert(wbuf);
@@ -310,7 +310,7 @@ test_iocp_bufferevent_async(void *ptr)
 	char buf[128];
 	size_t n;
 
-	event_base_start_iocp(data->base);
+	event_base_start_iocp(data->base, 0);
 	port = event_base_get_iocp(data->base);
 	tt_assert(port);
 

test/regress_main.c

@@ -209,7 +209,7 @@ basic_test_setup(const struct testcase_t *testcase)
 			exit(1);
 	}
 	if (testcase->flags & TT_ENABLE_IOCP_FLAG) {
-		if (event_base_start_iocp(base)<0) {
+		if (event_base_start_iocp(base, 0)<0) {
 			event_base_free(base);
 			return (void*)TT_SKIP;
 		}