---
name: "pmdazswap"
section: "1"
platform: "linux"
package: "pcp"
version: "7.2.2-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/pmdazswap"
---

# pmdazswap(1)

zswap (compressed swap) PMDA

## NAME

**pmdazswap** - zswap (compressed swap) PMDA

## DESCRIPTION

**pmdazswap** is a Performance Metrics Domain Agent (PMDA) which exports metric values about compressed swap operation, as tracked by the **zswap** Linux kernel module.

Zswap is a lightweight compressed cache for swap pages. It takes pages that are in the process of being swapped out and attempts to compress them into a dynamically allocated RAM-based memory pool. Zswap trades CPU cycles for potentially reduced swap I/O. This tradeoff can also result in a performance improvement if reads from the compressed cache are faster than reads from a swap device.

This PMDA exports metrics about pool size, number of pages stored, and various counters for the reasons pages are rejected.

## INSTALLATION

Install the zswap PMDA by using the Install script as root:

```
# cd $PCP_PMDAS_DIR/zswap
# ./Install
```

To uninstall, do the following as root:

```
# cd $PCP_PMDAS_DIR/zswap
# ./Remove
```

**pmdazswap** is launched by [*pmcd*(1)](/pmcd/1.md) and should never be executed directly. The Install and Remove scripts notify [*pmcd*(1)](/pmcd/1.md) when the agent is installed or removed.

## FILES

- **$PCP\_PMDAS\_DIR/zswap/Install**

  installation script for the **pmdazswap** agent

- **$PCP\_PMDAS\_DIR/zswap/Remove**

  undo installation script for the **pmdazswap** agent

- **$PCP\_LOG\_DIR/pmcd/zswap.log**

  default log file for error messages from **pmdazswap**

## PCP ENVIRONMENT

Environment variables with the prefix **PCP\_** are used to parameterize the file and directory names used by **PCP**. On each installation, the file **/etc/pcp.conf** contains the local values for these variables. The **$PCP\_CONF** variable may be used to specify an alternative configuration file, as described in [*pcp.conf*(5)](/pcp.conf/5.md).

## SEE ALSO

[**PCPIntro**(1)](/PCPIntro/1.md) and [**pmcd**(1)](/pmcd/1.md).