Swap is not a replacement for RAM. It is not just slow. It is very-very-very slow. Even SSDs are 10^3 slower at random access with small 4K blocks. Swap is for allocated but unused memory. If the system tries to use swap as active memory, it is going to become unresponsive very quickly - 0.1% memory excess causes a 2x degradation, 1% - 10x degradation, 10% - 100x degradation.

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AtlasBarfed 8 hours ago | parent [-]

What is allocated but unused memory? That sounds like memory that will be used in the near future and we are scheduling in an annoying disk load when it is needed

You are of course highlighting the problem that virtual addressing was intended to over abstract memory resource usage, but it provides poor facilities for power users to finely prioritize memory usage.

The example of this is game consoles, which didn't have this layer. Game writers had to reserve parts of ram fur specific uses.

You can't do this easily in Linux afaik, because it is forcing the model upon you.

	▲	man8alexd 8 hours ago \| parent [-]
		Unused or Inactive memory is memory that hasn't been accessed recently. The kernel maintains LRU (least recently used) lists for most of its memory pages. The kernel memory management works on the assumption that the least recently used pages are least likely to be accessed soon. Under memory pressure, when the kernel needs to free some memory pages, it swaps out pages at the tail of the inactive anonymous LRU. Cgroup limits and OOM scores allow to prioritize memory usage on a per-process and per-process group basis. madvise(2) syscall allows to prioritize memory usage within a process.