...
| Code Block |
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omkd_max_requests |
MongoDB memory usage
MongoDB, in its default configuration, will use will use the larger of either 256 MB or ½ of (ram – 1 GB) for its cache size.
MongoDB cache size can be changed by adding the cacheSizeGB argument to the /etc/mongod.conf configuration file, as shown below.
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storage:
dbPath: /var/lib/mongodb
journal:
enabled: true
wiredTiger:
engineConfig:
cacheSizeGB: 1 |
Here is an interesting information regarding how MongoDB reserves memory for internal cache and WiredTiger, the underneath technology. Also some adjustment that can be done: https://dba.stackexchange.com/questions/148395/mongodb-using-too-much-memory
Server examples
Stressed system
| Status | ||||
|---|---|---|---|---|
|
System information:
| Name | Value |
|---|---|
| nmisd_max_workers | 10 |
| omkd_workers | 4 |
| omkd_max_requests | 500 |
| Nodes | 406 |
| Active Nodes | 507 |
| SO | Ubuntu 18.04.3 LTS |
This is how the server memory graphs looks in a stressed system:
NMIS process keeps stable, is not using more than 120 mb, and the process was stopped - probably killed for the system due to high memory usage:
| Status | ||||
|---|---|---|---|---|
|
The OMK process has more fluctuations and higher memory usage - peaks up to 800 mb. The memory trend is to raise:
And mongod keeps using a lot of memory - 3GB, as configured - but it is stable:
Normal system
This is