mirror of
https://github.com/itzg/docker-minecraft-server.git
synced 2024-06-07 19:40:43 +00:00
133 lines
4.3 KiB
Markdown
133 lines
4.3 KiB
Markdown
# JVM Options
|
|
|
|
## Memory Limit
|
|
|
|
By default, the image declares an initial and maximum Java memory-heap limit of 1 GB. There are several ways to adjust the memory settings:
|
|
|
|
- `MEMORY`: "1G" by default, can be used to adjust both initial (`Xms`) and max (`Xmx`) memory heap settings of the JVM
|
|
- `INIT_MEMORY`: independently sets the initial heap size
|
|
- `MAX_MEMORY`: independently sets the max heap size
|
|
|
|
The values of all three are passed directly to the JVM and support format/units as `<size>[g|G|m|M|k|K]`.
|
|
|
|
!!! example "Using docker run"
|
|
|
|
```
|
|
-e MEMORY=2G
|
|
```
|
|
|
|
or to use init and max memory:
|
|
|
|
```
|
|
-e INIT_MEMORY=1G -e MAX_MEMORY=4G
|
|
```
|
|
|
|
!!! example "Using compose file"
|
|
|
|
```
|
|
environment:
|
|
MEMORY: 2G
|
|
```
|
|
|
|
or to use init and max memory:
|
|
|
|
```
|
|
environment:
|
|
INIT_MEMORY: 1G
|
|
MAX_MEMORY: 4G
|
|
```
|
|
|
|
To let the JVM calculate the heap size from the container declared memory limit, unset `MEMORY` with an empty value, such as `-e MEMORY=""`. By default, the JVM will use 25% of the container memory limit as the heap limit; however, as an example the following would tell the JVM to use 75% of the container limit of 4GB of memory:
|
|
|
|
!!! example "MaxRAMPercentage using compose file"
|
|
|
|
```
|
|
environment:
|
|
MEMORY: ""
|
|
JVM_XX_OPTS: "-XX:MaxRAMPercentage=75"
|
|
deploy:
|
|
limits:
|
|
memory: 4G
|
|
```
|
|
|
|
!!! important
|
|
The settings above only set the Java **heap** limits. Memory resource requests and limits on the overall container should also account for non-heap memory usage. An extra 25% is [a general best practice](https://dzone.com/articles/best-practices-java-memory-arguments-for-container).
|
|
|
|
## Extra JVM Options
|
|
|
|
General JVM options can be passed to the Minecraft Server invocation by passing a `JVM_OPTS`
|
|
environment variable. The JVM requires `-XX` options to precede `-X` options, so those can be declared in `JVM_XX_OPTS`. Both variables are space-delimited, raw JVM arguments.
|
|
|
|
```
|
|
docker run ... -e JVM_OPTS="-someJVMOption someJVMOptionValue" ...
|
|
```
|
|
|
|
**NOTE** When declaring `JVM_OPTS` in a compose file's `environment` section with list syntax, **do not** include the quotes:
|
|
|
|
```yaml
|
|
environment:
|
|
- EULA=true
|
|
- JVM_OPTS=-someJVMOption someJVMOptionValue
|
|
```
|
|
|
|
Using object syntax is recommended and more intuitive:
|
|
|
|
```yaml
|
|
environment:
|
|
EULA: "true"
|
|
JVM_OPTS: "-someJVMOption someJVMOptionValue"
|
|
# or
|
|
# JVM_OPTS: -someJVMOption someJVMOptionValue
|
|
```
|
|
|
|
As a shorthand for passing several system properties as `-D` arguments, you can instead pass a comma separated list of `name=value` or `name:value` pairs with `JVM_DD_OPTS`. (The colon syntax is provided for management platforms like Plesk that don't allow `=` inside a value.)
|
|
|
|
For example, instead of passing
|
|
|
|
```yaml
|
|
JVM_OPTS: -Dfml.queryResult=confirm -Dname=value
|
|
```
|
|
|
|
you can use
|
|
|
|
```yaml
|
|
JVM_DD_OPTS: fml.queryResult=confirm,name=value
|
|
```
|
|
|
|
## Enable Remote JMX for Profiling
|
|
|
|
To enable remote JMX, such as for profiling with VisualVM or JMC, set the environment variable `ENABLE_JMX` to "true", set `JMX_HOST` to the IP/host running the Docker container, and add a port forwarding of TCP port 7091, such as:
|
|
|
|
!!! example
|
|
|
|
With `docker run`
|
|
|
|
```
|
|
-e ENABLE_JMX=true -e JMX_HOST=$HOSTNAME -p 7091:7091
|
|
```
|
|
|
|
If needing to map to a different port, then also set the environment variable `JMX_PORT` to the desired host port.
|
|
|
|
!!! example
|
|
|
|
With a compose file:
|
|
|
|
```yaml
|
|
environment:
|
|
ENABLE_JMX: true
|
|
JMX_HOST: ${HOSTNAME}
|
|
JMX_PORT: "7092"
|
|
ports:
|
|
- "7092:7092"
|
|
```
|
|
|
|
## Enable Aikar's Flags
|
|
|
|
[Aikar has done some research](https://aikar.co/2018/07/02/tuning-the-jvm-g1gc-garbage-collector-flags-for-minecraft/) into finding the optimal JVM flags for GC tuning, which becomes more important as more users are connected concurrently. [PaperMC also has an explanation](https://docs.papermc.io/paper/aikars-flags) of what the JVM flags are doing.
|
|
|
|
The set of flags documented there can be added using
|
|
|
|
-e USE_AIKAR_FLAGS=true
|
|
|
|
When `MEMORY` is greater than or equal to 12G, then the Aikar flags will be adjusted according to the article.
|