[C++] Set CPU affinity
Sticking to a single processor improves the performance while
we are running only a single thread.
diff --git a/affinity.cc b/affinity.cc
new file mode 100644
index 0000000..0743f94
--- /dev/null
+++ b/affinity.cc
@@ -0,0 +1,50 @@
+// Copyright 2016 Google Inc. All rights reserved
+//
+// 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.
+
+#include "affinity.h"
+
+#include "flags.h"
+#include "log.h"
+
+#ifdef __linux__
+
+#include <sched.h>
+
+void SetAffinityForSingleThread() {
+ cpu_set_t cs;
+ CPU_ZERO(&cs);
+ int n = g_flags.num_cpus / 2;
+ CPU_SET(n, &cs);
+ if (n > 1)
+ CPU_SET(n + 1, &cs);
+ if (sched_setaffinity(0, sizeof(cs), &cs) < 0)
+ WARN("sched_setaffinity: %s", strerror(errno));
+}
+
+void SetAffinityForMultiThread() {
+ cpu_set_t cs;
+ CPU_ZERO(&cs);
+ for (int i = 0; i < g_flags.num_cpus; i++) {
+ CPU_SET(i, &cs);
+ }
+ if (sched_setaffinity(0, sizeof(cs), &cs) < 0)
+ WARN("sched_setaffinity: %s", strerror(errno));
+}
+
+#else
+
+void SetAffinityForSingleThread() {}
+void SetAffinityForMultiThread() {}
+
+#endif