Manual:$wgUseTurckShm

Memcached settings: $wgUseTurckShm
Use Turck MMCache shared memory.
Introduced in version:1.4.0 (r4882)
Removed in version:1.5.0
Allowed values:(boolean)
Default value:false

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Use Turck MMCache shared memory.

You can use this for persistent caching where your wiki runs on a single server. Enabled by default if Turck is installed. Mutually exclusive with memcached, memcached is used if both are specified.