+ // Each GC thread is responsible for following roots from the
+ // Capability of the same number. There will usually be the same
+ // or fewer Capabilities as GC threads, but just in case there
+ // are more, we mark every Capability whose number is the GC
+ // thread's index plus a multiple of the number of GC threads.
+ for (i = gct->thread_index; i < n_capabilities; i += n_gc_threads) {