**🔧 Unlocking system performance: A practical guide to tuning PCP on Fedora & RHEL** By Suraj Rajendra Patil (Fedora ID: suraj522) *Performance Co-Pilot (PCP)* is a robust framework for collecting, monitoring, and analyzing system performance metrics. Available out of the box on Fedora and RHEL, it allows administrators to gather a wide array of data with minimal configuration. But is the default setup right for your use case? Often, it’s not. While PCP’s defaults strike a balance between data granularity and overhead, production workloads vary widely. This guide walks you through tuning *PCP’s pmlogger* service to better fit your needs—whether you're debugging performance issues or running on constrained hardware. ### ✅ Prerequisites: Getting PCP up and running First, install the PCP packages: ``` $ sudo dnf install pcp pcp-system-tools ``` Then enable and start the core services: ``` $ sudo systemctl enable --now pmcd.service $ sudo systemctl enable --now pmlogger.service ``` Verify both services are running: ``` $ systemctl status pmcd pmlogger ``` ### 🔍 Understanding pmlogger and its configuration *PCP* consists of two main components: * *pmcd*: collects live performance metrics from various agents. * *pmlogger*: archives these metrics over time for analysis. The behavior of *pmlogger* is controlled by files in */etc/pcp/pmlogger/control.d/*. The most relevant is *local*, which contains command-line options for how logging should behave. Sample configuration: ``` $ cat /etc/pcp/pmlogger/control.d/local ``` You’ll see a line like: ``` localhost y y /usr/bin/pmlogger -h localhost ... -t 10s -m note ``` The *-t 10s* flag defines the logging interval—every 10 seconds in this case. ### 🔧 Scenario 1: High-frequency monitoring for deep analysis Use case: Debugging a transient issue on a production server. Goal: Change the logging interval from 10 seconds to 1 second. Edit the file: ``` $ sudo nano /etc/pcp/pmlogger/control.d/local ``` Change *-t 10s* to *-t 1s*. Restart the logger: ``` $ sudo systemctl restart pmlogger.service ``` Verify: ``` $ ps aux | grep '[p]mlogger -h localhost' $ pminfo -f ``` Expected output snippet: ``` records: 10, interval: 0:00:01.000 ``` ### đŸȘ¶ Scenario 2: Lightweight monitoring for constrained systems Use case: Monitoring on a small VM or IoT device. Goal: Change the logging interval to once every 60 seconds. Edit the same file: ``` $ sudo nano /etc/pcp/pmlogger/control.d/local ``` Change *-t 10s* to *-t 60s*. Restart the logger: ``` $ sudo systemctl restart pmlogger.service ``` Confirm: ``` $ ps aux | grep '[p]mlogger -h localhost' $ pminfo -f ``` Expected output: ``` records: 3, interval: 0:01:00.000 ``` ### đŸ§č Managing data retention: logs, size, and cleanup *PCP* archives are rotated daily by a cron-like service. Configuration lives in: ``` $ cat /etc/sysconfig/pmlogger ``` Default values: ``` PCP_MAX_LOG_SIZE=100 PCP_MAX_LOG_VERSIONS=14 ``` * *PCP\_MAX\_LOG\_VERSIONS*: number of daily logs to keep. * *PCP\_MAX\_LOG\_SIZE*: total archive size (in MB). Goal: Keep logs for 30 days. Edit the file: ``` $ sudo nano /etc/sysconfig/pmlogger ``` Change: ``` PCP_MAX_LOG_VERSIONS=30 ``` No service restart is required. Changes apply during the next cleanup cycle. ### 🏁 Final thoughts *PCP* is a flexible powerhouse. With just a few changes, you can transform it from a general-purpose monitor into a specialized tool tailored to your workload. Whether you need precision diagnostics or long-term resource tracking, tuning *pmlogger* gives you control and confidence. So go ahead—open that config file and start customizing your system's performance story. *Note: This article is dedicated to my wife, Rupali Suraj Patil, who inspires me every day.*