# Limiting process resource usage in AL2023 using cgroups
<a name="resource-limiting-raw-cgroups"></a>

 While it is recommended to use [Resource control with systemd](resource-limiting-systemd.md), this section covers basic usage of the base `libcgroup-tools` utilities to limit CPU and memory usage of processes. Both methods are alternatives to using the [`cpulimit`](epel.md#cpulimit) utility, previously found in [EPEL](epel.md). 

 The example below covers running the `stress-ng` stress test (from the `stress-ng` package) while limiting its CPU and memory usage using utilities from the `libcgroup-tools` package, and the tunables in `sysfs`. 

**Use `libcgroup-tools` on the command line to limit resource usage**

1.  Install the `libcgroup-tools` package. 

   ```
   [ec2-user ~]$ sudo dnf install libcgroup-tools
   ```

1.  Create a `cgroup` with the `memory` and `cpu` controllers, and give it a name (`our-example-limits`). Using the `-a` and `-t` options to allow the `ec2-user` user to control the tunables of the `cgroup` 

   ```
   [ec2-user ~]$ sudo cgcreate -a ec2-user -t ec2-user -g memory,cpu:our-example-limits
   ```

    There is now a `/sys/fs/cgroup/our-example-limits/` directory that contains files that can be used to control each tunable. 
**Note**  
 Amazon Linux 2 uses `cgroup-v1` rather `cgroup-v2` which is used on AL2023. On AL2, the `sysfs` paths are different, and there will be `/sys/fs/cgroup/memory/our-example-limits` and `/sys/fs/cgroup/cpu/our-example-limits` directories owned by `ec2-user` which contain files that can be used to control the limits of the `cgroup`. 

1.  Limit memory usage of all processes in our `cgroup` to 100 million bytes. 

   ```
   [ec2-user ~]$ echo 100000000 > /sys/fs/cgroup/our-example-limits/memory.max
   ```
**Note**  
 Amazon Linux 2 uses `cgroup-v1` rather than the `cgroup-v2` that Amazon Linux 2023 uses. This means that some tunables are different. To limit memory usage on AL2, the below tunable is used instead.   

   ```
   [ec2-user ~]$ echo 10000000 > /sys/fs/cgroup/memory/our-example-limits/memory.limit_in_bytes
   ```

1.  Limit CPU usage of all processes in our `cgroup` to 10%. The format of the `cpu.max` file is `$MAX $PERIOD`, limiting the group to consuming `$MAX` for every `$PERIOD`. 

   ```
   [ec2-user ~]$ echo 10000 100000 > /sys/fs/cgroup/our-example-limits/cpu.max
   ```

    Amazon Linux 2 uses `cgroup-v1` rather than the `cgroup-v2` that Amazon Linux 2023 uses. This means that some tunables are different, including how to limit CPU usage. 

1.  The below example runs `stress-ng` (which can be installed by running `dnf install -y stress-ng`) in the `our-example-limits` cgroup. While the `stress-ng` command is running, you can observe using `top` that it is limited to 10% of CPU time. 

   ```
   [ec2-user ~]$ sudo cgexec -g memory,cpu:our-example-limits stress-ng --cpu 1
   ```

1. Clean up by removing the cgroup

   ```
   [ec2-user ~]$ sudo cgdelete -g memory,cpu:our-example-limits
   ```

 The [Linux Kernel documentation for `cgroup-v2`](https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html) contains extensive details about how they work. The documentation of the [cpu](https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#cpu) and [memory](https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory) controllers covers the details of how to use each tunable option.