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bpftrace PMDA

This PMDA exports metrics from bpftrace scripts. In combination with the PCP Plugin for Grafana this PMDA enables on-demand live performance analysis using eBPF. The Grafana plugin also supports the visualization of histograms collected by this PMDA.

Quickstart (using the command line interface)

Open /var/lib/pcp/pmdas/bpftrace/bpftrace.conf and enable dynamic scripts, then execute the following commands:

$ cd /var/lib/pcp/pmdas/bpftrace && sudo ./Install

$ pmstore -F bpftrace.control.register 'kretprobe:vfs_read { @bytes = hist(retval); }'

$ pminfo -f bpftrace.info.scripts
bpftrace.info.scripts
    inst [1 or "script100"] value "kretprobe:vfs_read { @bytes = hist(retval); }"

$ pminfo -f bpftrace.scripts.script100.data.bytes
bpftrace.scripts.script100.data.bytes
    inst [0 or "-inf--1"] value 409
    inst [1 or "0-0"] value 191
    inst [2 or "1-1"] value 1160
    inst [3 or "2-3"] value 85
    inst [4 or "4-7"] value 61
    inst [5 or "8-15"] value 431
    inst [6 or "16-31"] value 98

The autostart folder

bpftrace scripts in the autostart folder get executed and exported as PCP metrics on PMDA startup. Note that these scripts must be exclusive writeable by the root user for security reasons.

This is the recommended usage for production systems. Please note that bpftrace scripts can have a performance impact, therefore it is advisable to measure the performance impact before running bpftrace scripts on production systems.

Features

  • Start and stop multiple bpftrace scripts on demand.
  • Export bpftrace variables (eBPF maps) as PCP metrics:
    • single values, counters
    • maps, histograms
    • text output (by printf(), time() etc.)
  • Automatic removal of scripts whose values weren't requested in a specified time period.

Configuration

The configuration of this PMDA is stored in bpftrace.conf.

Note: for production systems, it is recommended to not enable dynamic scripts (this feature is disabled by default) and use the autostart folder instead.

Scripts Metadata

This PMDA supports the following metadata annotations, to be included in the bpftrace script as comments:

Named Scripts

// name: script_name

This annotation sets the name of a script. Metrics will be exported in the bpftrace.scripts.scriptname namespace. Named scripts will never be removed, even if their value isn't requested in a long time period.

Only export specific variables

// include: @bytes,@count

By default all bpftrace variables get exported as metrics. This annotation changes the default behavior and specifies which bpftrace variables should be exported. All other bpftrace variables will be ignored.

Tables

// table-retain-lines: 10

A common use case is to print tables in CSV format (using printf()), and display them as a table in Grafana. This setting controls how many data lines should be retained. The table header (the first line) will be preserved.

Thanks

Thanks to Alastair Robertson and all contributors of bpftrace.