allocators

page-based groupings

page ~ 2^10 bytes
1 byte = 8 bits
1 word ~ 8 bytes/word = 64 bits/word

1 page / 1 word ~ 2^7 words/page
2^7 words/page / 2^6 bits/word = 2^1 words

( assuming 1 byte = 8 bits )
so, given a 4 kbyte page size and 8 byte ( 64 bit ) word size,
a page of word size /granularity allocations would only need 2 words of bookkeeping