Initialize ELG with the number of affinitized cores

Package.swift

@@ -36,9 +36,12 @@ let package = Package(
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages which this package depends on.
+        .target(
+            name: "CLinuxHelpers",
+            dependencies: []),
         .target(
             name: "KituraNet",
-            dependencies: ["NIO", "NIOFoundationCompat", "NIOHTTP1", "NIOOpenSSL", "SSLService", "LoggerAPI", "NIOWebSocket"]),
+            dependencies: ["NIO", "NIOFoundationCompat", "NIOHTTP1", "NIOOpenSSL", "SSLService", "LoggerAPI", "NIOWebSocket", "CLinuxHelpers"]),
         .testTarget(
             name: "KituraNetTests",
             dependencies: ["KituraNet"]),

Sources/CLinuxHelpers/ProcessorAffinity.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright IBM Corporation 2018
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifdef __linux__
+
+#define _GNU_SOURCE
+#include <sched.h>
+#include <unistd.h>
+
+// Reference: https://stackoverflow.com/questions/10490756/how-to-use-sched-getaffinity-and-sched-setaffinity-in-linux-from-c
+int linux_sched_getaffinity() {
+    cpu_set_t mask;
+    long nproc, i, count = 0;
+
+    if (sched_getaffinity(0, sizeof(cpu_set_t), &mask) == -1) {
+        return -1;
+    } else {
+        nproc = sysconf(_SC_NPROCESSORS_ONLN);
+        for (i = 0; i < nproc; i++) {
+            if(CPU_ISSET(i, &mask))
+                count += 1;
+        }
+        return count;
+    }
+}
+
+#endif

Sources/CLinuxHelpers/include/ProcessorAffinity.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright IBM Corporation 2018
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#if __linux__
+int linux_sched_getaffinity();
+#endif

Sources/KituraNet/HTTP/HTTPServer.swift

@@ -21,6 +21,7 @@ import NIOOpenSSL
 import SSLService
 import LoggerAPI
 import NIOWebSocket
+import CLinuxHelpers
 
 /// An HTTP server that listens for connections on a socket.
 public class HTTPServer : Server {
@@ -66,11 +67,18 @@ public class HTTPServer : Server {
     private let maxPendingConnections = 100
 
     /// The event loop group on which the HTTP handler runs
-    let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
+    private let eventLoopGroup: MultiThreadedEventLoopGroup
 
     private var ctx: ChannelHandlerContext?
 
-    public init() { }
+    public init() {
+#if os(Linux)
+        let numberOfCores = Int(linux_sched_getaffinity())
+        self.eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: numberOfCores > 0 ? numberOfCores : System.coreCount)
+#else
+        self.eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
+#endif
+    }
 
     /// SSL cert configs for handling client requests
     public var sslConfig: SSLService.Configuration? {