Switch radix back from 6x6 to 9x4

This was originally to make radix_node rcu_freed, but that didn't happen. 9x4 makes each radix_node one page and thus easier to allocate.

Switch radix back from 6x6 to 9x4
6997e5ae · Austin Clements · 879bf6db · 6997e5ae
--- a/include/radix.hh
+++ b/include/radix.hh
@@ -6,7 +6,7 @@

 #include "gc.hh"

-enum { bits_per_level = 6 };
+enum { bits_per_level = 9 };
 enum { key_bits = 36 };
 enum { radix_levels = (key_bits + bits_per_level - 1) / bits_per_level };