1 files changed, 60 insertions, 0 deletions
diff --git a/third_party/nix/src/libutil/affinity.cc b/third_party/nix/src/libutil/affinity.cc
new file mode 100644
index 0000000000..03fbe12439
--- /dev/null
+++ b/third_party/nix/src/libutil/affinity.cc
@@ -0,0 +1,60 @@
+#include "libutil/affinity.hh"
+
+#include <glog/logging.h>
+
+#include "libutil/types.hh"
+#include "libutil/util.hh"
+
+#if __linux__
+#include <sched.h>
+#endif
+
+namespace nix {
+
+#if __linux__
+static bool didSaveAffinity = false;
+static cpu_set_t savedAffinity;
+#endif
+
+void setAffinityTo(int cpu) {
+#if __linux__
+  if (sched_getaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1) {
+    return;
+  }
+
+  didSaveAffinity = true;
+  DLOG(INFO) << "locking this thread to CPU " << cpu;
+  cpu_set_t newAffinity;
+  CPU_ZERO(&newAffinity);
+  CPU_SET(cpu, &newAffinity);
+  if (sched_setaffinity(0, sizeof(cpu_set_t), &newAffinity) == -1) {
+    LOG(ERROR) << "failed to lock thread to CPU " << cpu;
+  }
+#endif
+}
+
+int lockToCurrentCPU() {
+#if __linux__
+  int cpu = sched_getcpu();
+  if (cpu != -1) {
+    setAffinityTo(cpu);
+  }
+  return cpu;
+#else
+  return -1;
+#endif
+}
+
+void restoreAffinity() {
+#if __linux__
+  if (!didSaveAffinity) {
+    return;
+  }
+
+  if (sched_setaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1) {
+    LOG(ERROR) << "failed to restore affinity";
+  }
+#endif
+}
+
+}  // namespace nix