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-rw-r--r--nix/libutil/affinity.cc55
1 files changed, 55 insertions, 0 deletions
diff --git a/nix/libutil/affinity.cc b/nix/libutil/affinity.cc
new file mode 100644
index 0000000000..3e21f43a2e
--- /dev/null
+++ b/nix/libutil/affinity.cc
@@ -0,0 +1,55 @@
+#include "types.hh"
+#include "util.hh"
+#include "affinity.hh"
+
+#if HAVE_SCHED_H
+#include <sched.h>
+#endif
+
+namespace nix {
+
+
+#if HAVE_SCHED_SETAFFINITY
+static bool didSaveAffinity = false;
+static cpu_set_t savedAffinity;
+#endif
+
+
+void setAffinityTo(int cpu)
+{
+#if HAVE_SCHED_SETAFFINITY
+ if (sched_getaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1) return;
+ didSaveAffinity = true;
+ printMsg(lvlDebug, format("locking this thread to CPU %1%") % cpu);
+ cpu_set_t newAffinity;
+ CPU_ZERO(&newAffinity);
+ CPU_SET(cpu, &newAffinity);
+ if (sched_setaffinity(0, sizeof(cpu_set_t), &newAffinity) == -1)
+ printMsg(lvlError, format("failed to lock thread to CPU %1%") % cpu);
+#endif
+}
+
+
+int lockToCurrentCPU()
+{
+#if HAVE_SCHED_SETAFFINITY
+ int cpu = sched_getcpu();
+ if (cpu != -1) setAffinityTo(cpu);
+ return cpu;
+#else
+ return -1;
+#endif
+}
+
+
+void restoreAffinity()
+{
+#if HAVE_SCHED_SETAFFINITY
+ if (!didSaveAffinity) return;
+ if (sched_setaffinity(0, sizeof(cpu_set_t), &savedAffinity) == -1)
+ printMsg(lvlError, "failed to restore affinity %1%");
+#endif
+}
+
+
+}