Chapter 21. Performance

This chapter lists the most notable changes to performance between RHEL 8 and RHEL 9.

21.1. Notable changes to performance

The sadf(1) tool now generates PCP archives from native sadc(1) archives

Starting in RHEL 9, the sadf(1) tool provided by the sysstat package can generate PCP archives from native sadc(1) archives.

By default, when the `- flag is used with sadc(1), sadc(1) writes the data to the standard system activity daily data file. This file is named saDD and is located in the /var/log/sa directory by default. Conversely, when no input datafile is specified, the sadf(1) tool uses the standard system activity daily data file to generate archives. Pass numbers as an argument to tell sadf(1) to generate archives from data recorded that specified number of days in the past.

  • To generate a PCP archive from an sadc(1) archive recorded 2 days ago, run:

    # sadf -l -O pcparchive=/tmp/recording -2
  • To show a list of metrics in the PCP archive generated from an sadc(1) archive archive, run:

    $ pminfo --archive /tmp/recording
    Disk.dev.avactive
    Disk.dev.read
    Disk.dev.write
    Disk.dev.blkread
    [...]
  • To show the timespace of the archive and hostname of the PCP archive generated from an sadc(1) archive

    $ pmdumplog --label /tmp/recording
    Log Label (Log Format Version 2)
    Performance metrics from host shard
            commencing Tue Jul 20 00:10:30.642477 2021
            ending     Wed Jul 21 00:10:30.222176 2021
  • You can then analyze the PCP archive generated from an sadc(1) archive by using PCP commands, for example:

    $ pmchart --archive /tmp/recording