I have slow HDD and 5.5 GB of RAM, and thus I'm using zram and no any disk swap.
According to my observations, the lack of disk cache has much worse impact on performance than active swapping. While swapping freezes only processes that quickly increase RAM usage or were swapped out because of inactivity, accidental reducing of disk cache freezes many of processes that rely on disk read operations and increases Load Average to >4x of the cores number.
So it would be better to always have at least 0.5 GB of RAM reserved for disk read cache under any circumstances. However, even with
vm.swappiness=100 it is not always kept up: if some process is quickly increasing the RAM usage, or there are already several gigabytes in swap, amount of free RAM still can be reduced to 100–300 MB.
Does the Linux kernel have any explicit handles to set a minimal amount of RAM that should be always reserved for