linux: Set CONFIG_NO_HZ_FULL=y.

CONFIG_NO_HZ_FULL=y should be set to enable the `nohz_full=` and
`rcu_nocbs=` options. These carry no additional performance penalty
compared to CONFIG_NO_HZ_IDLE and behaves like it by default,
but allows disabling the tick interrupts on cores for power or
performance reasons.

[Debian][1] also applied the change to all their kernels.
Like the Kernel says: "If you're a distro say Y."

[1]: f6aad27f05

pkgs/os-specific/linux/kernel/common-config.nix

@@ -114,6 +114,12 @@ let
       IOSCHED_BFQ = whenAtLeast "4.12" module;
     };
 
+
+    timer = {
+      # Enable Full Dynticks System.
+      NO_HZ_FULL = yes;
+    };
+
     # Enable NUMA.
     numa = {
       NUMA  = option yes;