As part of the memory management changes expected to be merged for the upcoming Linux 6.11 cycle is allowing more fine-tuned control over the swappiness setting used to determine how aggressively pages are swapped out of physical system memory and into the on-disk swap space.
With the new code from Meta, a swappiness argument is supported for memory.reclaim. This effectively allows more finer-grained control over the swapiness behavior without overriding the global swappiness setting.
Actually… as a former DBA on large databases, you typically want to minimize swapping on a dedicated database system. Most database engines do a much better job at keeping useful data in memory than the Linux kernel’s file caching, which is agnostic about what your files contain. There are some exceptions, like elasticsearch which almost entirely relies on the Linux filesystem cache for buffering I/O.
Anyway, database engines have query optimizers to determine the optimal path to resolve a query, but they rely on it that the buffers that they consider to be “in memory” are actually residing in physical memory, and not sitting in a swapfile somewhere.
So typically, on a large database system the vendor recommendation will be to set
vm.swappiness=0to minimize memory pressure from filesystem caching, and to set the database buffers as high as the amount of memory you have in your system minus a small amount for the operating system.