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) and should never be executed directly. The Install and Remove scripts notify pmcd(1) 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).