[core] Fix usage of sched_setaffinity() and disable it for now as it seems to impose a little performance hit

include/lighttpd/server.h

@@ -68,6 +68,10 @@ struct liServer {
 	liWorker *main_worker;
 	guint worker_count;
 	GArray *workers;
+#ifdef LIGHTY_OS_LINUX
+	cpu_set_t affinity_mask; /** cpus used by workers */
+	guint affinity_cpus;     /** total number of cpus in affinity_mask */
+#endif
 	GArray *ts_formats;      /** array of (GString*), add with li_server_ts_format_add() */
 
 	struct ev_loop *loop;

include/lighttpd/sys-process.h

@@ -13,5 +13,9 @@
 #include <unistd.h>
 #endif
 
+#ifdef LIGHTY_OS_LINUX
+#include <sched.h>
+#endif
+
 #endif
 

src/main/plugin_core.c

@@ -9,8 +9,6 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 
-#include <sched.h>
-
 static liAction* core_list(liServer *srv, liWorker *wrk, liPlugin* p, liValue *val, gpointer userdata) {
 	liAction *a;
 	guint i;
@@ -1550,29 +1548,37 @@ static const liPluginAngel angelcbs[] = {
 
 	{ NULL, NULL }
 };
+#include <sys/types.h>
 
 static void plugin_core_prepare_worker(liServer *srv, liPlugin *p, liWorker *wrk) {
 	UNUSED(p);
 
-#ifdef LIGHTY_OS_LINUX
+
+#if defined(LIGHTY_OS_LINUX) && 0
 	/* sched_setaffinity is only available on linux */
-	{
+	if (srv->affinity_cpus != 0) {
+		gint cpu;
+		guint cpu_nth;
 		cpu_set_t mask;
 
-		if (0 != sched_getaffinity(0, sizeof(mask), &mask)) {
-			ERROR(srv, "couldn't get cpu affinity mask: %s", g_strerror(errno));
-		} else {
-			guint cpus = 0;
-			while (CPU_ISSET(cpus, &mask)) cpus++;
-			if (cpus) {
+		/* bind worker to n-th cpu */
+		for (cpu_nth = 0, cpu = 0; cpu < CPU_SETSIZE; cpu++) {
+			//g_print("wrk: %u cpu: %d\n", wrk->ndx, cpu);
+			if (!CPU_ISSET(cpu, &srv->affinity_mask))
+				continue;
+
+			if ((wrk->ndx % srv->affinity_cpus) == cpu_nth) {
 				CPU_ZERO(&mask);
-				CPU_SET(wrk->ndx % cpus, &mask);
-				if (0 != sched_setaffinity(0, sizeof(mask), &mask)) {
+				CPU_SET(wrk->ndx % srv->affinity_cpus, &mask);
+				DEBUG(srv, "binding worker #%u to cpu #%u", wrk->ndx+1, wrk->ndx % srv->affinity_cpus);
+				if (0 != sched_setaffinity(0, sizeof(srv->affinity_mask), &mask)) {
 					ERROR(srv, "couldn't set cpu affinity mask: %s", g_strerror(errno));
 				}
-			} else {
-				ERROR(srv, "%s", "cpu 0 not enabled, no affinity set");
+
+				break;
 			}
+
+			cpu_nth++;
 		}
 	}
 #else

src/main/server.c

@@ -175,6 +175,20 @@ liServer* li_server_new(const gchar *module_dir, gboolean module_resident) {
 	srv->io_timeout = 300; /* default I/O timeout */
 	srv->keep_alive_queue_timeout = 5;
 
+#ifdef LIGHTY_OS_LINUX
+	/* sched_getaffinity is only available on linux */
+	if (0 != sched_getaffinity(0, sizeof(srv->affinity_mask), &srv->affinity_mask)) {
+		ERROR(srv, "couldn't get cpu affinity mask: %s", g_strerror(errno));
+	} else {
+		/* how many cpus do we have */
+		gint cpu;
+		for (cpu = 0; cpu < CPU_SETSIZE; cpu++) {
+			if (CPU_ISSET(cpu, &srv->affinity_mask))
+				srv->affinity_cpus++;
+		}
+	}
+#endif
+
 	return srv;
 }