High swap usage on your primary server or replica in Puppet Enterprise

You get errors, warnings, or messages that Puppet processes are using a high percentage of swap space on your primary server or replica.

Version and installation information

PE version: All supported
OS: Linux

• If you need assistance with your swap file or swappiness, get in touch with your OS support vendor.
• We do not provide support for third-party utilities.

Solution

Puppet Enterprise does not control how memory is handled on a Linux server. The Linux kernel copies chunks of RAM into swap, allowing processes that require more memory than what’s physically available. Swapping occurs during low memory conditions. Learn more about swap in this Red Hat article, under Introduction (requires a Red Hat subscription.)

Having high swap usage is not in itself an issue, but if swap usage is consistently high, you might have memory issues. You can address them by adding more memory, running fewer processes, creating or adjusting swap file use, or checking for bugs that affect OS memory. Learn more about how to fix swap issues (requires a Red Hat subscription.)

The rate at which swapping occurs is a more useful indicator of a memory performance issue than high swap usage is. A high percentage of swap used means that the kernel decided to use swap at some point in time, but may not indicate an issue at present. For example, if the processes using swap have completed, the kernel will not remove swapped out pages if it no longer needs to use swap. However, a high rate of swapping is a better indicator of memory issues that are frequently causing the kernel to swap. You can use sar, part of sysstat utilities, to check the rate of swap file operations.

You can influence how swap is working by adjusting the swappiness parameter in your OS. To increase how much your kernel swaps set swappiness higher, increasing memory performance at the expense of I/O performance. To swap out less often, set it lower, increasing I/O performance at the expense of memory performance. Learn more about swappiness.

Even though PE doesn’t handle memory directly, load from Puppet services can affect swap. If swapping occurs frequently, use the puppetlabs-puppet_operational_dashboards module to determine if Puppet metrics correlate with swap activity.