/*    hv.c   */

#define HV_MAX_LENGTH_BEFORE_SPLIT 14

...

Perl_hv_common( ... )
{
            ...

            while ((counter = HeNEXT(counter)))
                n_links++;

            if (n_links > HV_MAX_LENGTH_BEFORE_SPLIT) {
                /* Use only the old HvKEYS(hv) > HvMAX(hv) condition to limit
                   bucket splits on a rehashed hash, as we're not going to
                   split it again, and if someone is lucky (evil) enough to
                   get all the keys in one list they could exhaust our memory
                   as we repeatedly double the number of buckets on every
                   entry. Linear search feels a less worse thing to do.  */
                hsplit(hv);
            }

            ...
}