I am trying to improve performance (responsivity) of a webserver during rare events of high memory utilization (90%...) where it starts to swap a lot, in order to help manual intervening faster and less error prone. I can't add more RAM to the machine (32G RAM + 6G swap partition).
One way to improve performance in such a situation is using compressed swap caching in RAM, so that the system uses RAM more efficiently and the impact of I/O waits for slow nonvolatile memory decreases.
Older research from 1999 [1] indicates that the faster the CPU compared to I/O operations, the greater the benefits of compressed swap cache and this should get even better as CPUs get faster. It is recommended to use swap compression if using rotational disks.
I wonder whether this advice to increase performance still holds true for servers that have only SSD drives. Here the I/O operations are much faster, so the benefit is lower than with rotational disks.
An implementation of this functionality was introduced in Linux 3.11 via zswap in 2012 [2]. Does anybody have experience with it on a server, is there also a benefit when using purely SSD drives?
[1] https://www.usenix.org/legacy/event/usenix99/full_papers/wilson/wilson.pdf
[2] https://events.static.linuxfound.org/sites/events/files/slides/tmc_sjennings_linuxcon2013.pdf