> ## Documentation Index
> Fetch the complete documentation index at: https://docs.coreweave.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Manage memory with cache-dropper

> Use cache-dropper to manage memory between exclusive Slurm jobs on a node

This page explains how to use the `cache-dropper` sidecar to flush the Linux page cache between exclusive Slurm jobs on a SUNK compute node. It's intended for cluster administrators and job authors who need to mitigate memory fragmentation in CPU-intensive training workloads.

Between exclusive jobs on a node, dropping the page cache can improve performance and lower memory access times caused by memory fragmentation. Memory fragmentation can lead to Out of Memory (OOM) errors and slowdowns in CPU-intensive training jobs.

SUNK includes a sidecar container, `cache-dropper`, to handle page cache flushes. This container runs in privileged mode, which lets it drop the cache without requiring the main `slurmd` container to run as privileged. The sidecar checks for the presence of a [specific trigger file](#drop-the-page-cache-with-a-slurm-job) and drops the page cache if that file appears. The `cache-dropper` sidecar writes to the `drop_caches` [`sysctl`](https://www.kernel.org/doc/Documentation/sysctl/vm.txt) file to free both page cache and reclaimable slab objects.

Dropping the cache is a non-destructive operation, but it can incur additional CPU and I/O overhead as dropped objects are recreated.

## Enable the `cache-dropper` sidecar in the Slurm chart

To enable the `cache-dropper` sidecar, set `.compute.cacheDropper.enabled` to `true` in the [Slurm `values.yaml` file](/products/sunk/reference/slurm-parameters).

When enabled, `cache-dropper` is present in every compute pod. It periodically checks for the existence of the `/run/enroot/drop_caches` file as a signal to proceed. If this file exists, it triggers the cache drop operation.

## Drop the page cache with a Slurm job

After the sidecar is enabled, individual Slurm jobs trigger a cache drop by creating the trigger file the sidecar watches for.

To use `cache-dropper`, add the following `touch` command to a Slurm job script:

```bash theme={"system"}
touch /run/enroot/drop_caches
```

The cache drops each time the job runs this command. With the sidecar enabled and the trigger in place, jobs that include this command release the page cache before subsequent work runs on the node.