Vm.max_map_count recommendations, mongodb 6/7?

Hi @Derek_Cox

The full log output suggests the recommended value for the configured system. Check the log or use db.adminCommand({getLog: 'startupWarnings'}).log.forEach(l => printjson(l))

If the Operations Checklist, UNIX ulimit Settings and Production Notes were followed then this value should be 102400.

This is derived from net.maxIncomingConnections * 2

The default net.maxIncomingConnections per the below should be 64000 * 0.8

64000 from the ulimit set(this is usually done in the mongod.service file for RPM and deb installs)

https://www.mongodb.com/docs/manual/reference/configuration-options/#mongodb-setting-net.maxIncomingConnections

net.maxIncomingConnections

Type: integer

Default (Windows): 1,000,000

Default (Linux): (RLIMIT_NOFILE) * 0.8

https://github.com/mongodb/mongo/blob/e1aa498db8bee013a82646b02f04ee878e0e4bbf/src/mongo/db/startup_warnings_mongod.cpp#L286

size_t requiredMapCount = 2 * maxConns;

nofile 64000 is a good starting point per

https://www.mongodb.com/docs/manual/reference/ulimit/

Which would yield 102400 for vm.max_map_count

For the system, if mongod were running native from installation repos nofile would be set to 64000 for the systemd unit file.

As it is running in container that change would have to be made in docker-compose or docker run instead.