1 files changed, 66 insertions, 0 deletions
diff --git a/src/affinity.cc b/src/affinity.cc
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+++ b/src/affinity.cc
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+// 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.
+
+// +build ignore
+
+#include "affinity.h"
+
+#include "flags.h"
+#include "log.h"
+
+#ifdef __linux__
+
+#include <sched.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <random>
+
+void SetAffinityForSingleThread() {
+  cpu_set_t cs;
+  CPU_ZERO(&cs);
+  std::random_device generator;
+  std::uniform_int_distribution<int> distribution(0, g_flags.num_cpus - 1);
+  int cpu = distribution(generator);
+
+  // Try to come up with a CPU and one close to it. This should work on most
+  // hyperthreaded system, but may be less optimal under stranger setups.
+  // Choosing two completely different CPUs would work here as well, it's just a
+  // couple percent faster if they're close (and still faster than letting the
+  // scheduler do whatever it wants).
+  cpu = cpu - (cpu % 2);
+  CPU_SET(cpu, &cs);
+  if (g_flags.num_cpus > 1)
+    CPU_SET(cpu + 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