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For further information about THP, see https://developerdocs.couchbase.com/documentation/server/current/install/thp-disable.html.

Swap Space

On Linux, swap space is used when the physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. Swappiness indicates how frequently a system uses the swap space based on RAM usage. The swappiness range is from 0 to 100 where, by default, most Linux platforms have swappiness set to 60. For the optimal Couchbase Server operations, set the swappiness to 0 (zero).

For further information about swap space, see  https://developerdocs.couchbase.com/documentation/server/5.1current/install/install-swap-space.html.