Demo: Swap, in a Box

Run

make
./swap
systemd-run --user --scope -p MemoryMax=64M ./swap

Swap has to be enabled (swapon --show).

Ask

• The boxed write still succeeded. Where did 193 MB go, and who decided?
• Reading it back took 8,424 major faults and two seconds. Why does each read push something else out?
• The program's code is the same in both runs. What did it see of all this?