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authorVincent Ambo <tazjin@google.com>2020-05-17T14·52+0100
committerVincent Ambo <tazjin@google.com>2020-05-17T14·52+0100
commit7994fd1d545cc5c876d6f21db7ddf9185d23dad6 (patch)
tree32dd695785378c5b9c8be97fc583e9dfc62cb105 /third_party/nix/src/libutil/affinity.cc
parentcf8cd640c1adf74a3706efbcb0ea4625da106fb2 (diff)
parent90b3b31dc27f31e9b11653a636025d29ddb087a3 (diff)
Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10' r/724
git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1adf74a3706efbcb0ea4625da106fb2
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10
Diffstat (limited to 'third_party/nix/src/libutil/affinity.cc')
-rw-r--r--third_party/nix/src/libutil/affinity.cc55
1 files changed, 55 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 000000000000..98f8287ada67
--- /dev/null
+++ b/third_party/nix/src/libutil/affinity.cc
@@ -0,0 +1,55 @@
+#include "types.hh"
+#include "util.hh"
+#include "affinity.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;
+    debug(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)
+        printError(format("failed to lock thread to CPU %1%") % 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)
+        printError("failed to restore affinity %1%");
+#endif
+}
+
+
+}