Slide 11 of 19
Notes:
Greedy policy - most fragmented segment cleaned first
cold segments stay around much longer
BUT - free space in cold segments are much valuable - they stay around longer
hot segment - data die quickly - so wait a little longer to get the free space even larger
how to find stability of a data in a segment:
assumption: older the data in a segment, longer it will remain unchanged
segment-usage table: # of live blocks + last modification time
