Linux Multi-Threaded "Swap Insanity"

Here is a helpful description of a problem that can be encountered on Linux using the NUMA (Non-Uniform Memory Architecture), often seen with MySQL.

In a nutshell, the machine may bog down with memory-swapping when total memory use is far below what is available, because the default policy is for a processor to prefer the memory in its own node even when swapping occurs.

The simplest solution is to use numactl --interleave.