Don't apply the CPU affinity hack to nix-shell (and other Perl programs)

As discovered by Todd Veldhuizen, the shell started by nix-shell has
its affinity set to a single CPU.  This is because nix-shell connects
to the Nix daemon, which causes the affinity hack to be applied.  So
we turn this off for Perl programs.

1 files changed, 5 insertions, 6 deletions

diff --git a/src/libutil/affinity.cc b/src/libutil/affinity.cc
index 7a6310cadb00..3e21f43a2e9d 100644
--- a/src/libutil/affinity.cc
+++ b/src/libutil/affinity.cc
@@ -33,13 +33,12 @@ void setAffinityTo(int cpu)
 int lockToCurrentCPU()
 {
 #if HAVE_SCHED_SETAFFINITY
-    if (getEnv("NIX_AFFINITY_HACK", "1") == "1") {
-        int cpu = sched_getcpu();
-        if (cpu != -1) setAffinityTo(cpu);
-        return cpu;
-    }
-#endif
+    int cpu = sched_getcpu();
+    if (cpu != -1) setAffinityTo(cpu);
+    return cpu;
+#else
     return -1;
+#endif
 }