P2P backup systems have become a novelty solution to ensure data availability. The key idea of P2P backup systems is to use the freememoryspace shared by peers to store data.
If it does not free enough heap space, it proceeds to collect higher generations until enough memory has been reclaimed.
如果它不能释放足够的堆空间，那么它就继续收集上一代，直到回收了足够的内存。
3
When free physical memory starts getting low, programs that have not used recently are moved from ram to paging space to help release physical memory for more real work.