Swap

Swap gives Linux a backing store for eligible memory pages that need not remain resident. It can preserve cold data while RAM serves active work, but it does not make the machine’s working set fit at RAM speed. The useful question is whether reclaim frees space without repeatedly stalling important tasks. Swap occupancy, swap traffic, and application progress answer different parts of that question. ...

When memory tightens, eligible cold pages may be reclaimed to swap. A zram swap device stores compressed pages in RAM, trading CPU work and memory overhead for potential headroom. The benefit depends on the workload; it is not a fixed amount of extra memory. ...