Adding Memory Bandwidth Monitor to Tmux Powerline

Using `pcm` to Monitor Memory Bandwidth

pcm-memory is a tool that can be used to monitor memory bandwidth in Linux. It is part of the pcm (Performance Counter Monitor) suite, which provides various performance monitoring capabilities.

With pcm tools installed, we can setup a script to monitor memory bandwidth. I save it to /usr/local/bin/monitor-memory:

#!/bin/bash
# monitor-memory - Memory bandwidth monitor using Intel PCM
# This script runs pcm-memory with sudo privileges

# Check if pcm-memory is available
if ! command -v pcm-memory &> /dev/null; then
    echo "Error: pcm-memory not found. Please install Intel PCM toolkit."
    exit 1
fi

# Check if running as root
if [[ "$EUID" -ne 0 ]]; then
    echo "Error: This script must be run as root."
    exit 1
fi

# Run pcm-memory with specified parameters
# -s: silent mode, no verbose output
# -csv: output in CSV format
# -nc: suppress detailed channel info
# -- sleep: workaround to run pcm-memory once
sudo pcm-memory -s -csv -nc -- sleep 0.01

# Note: The output format from pcm-memory typically includes many columns.
# The last three values should be read, write, total bandwidth in MB/s

Setting `sudo` Permissions for `monitor-memory`

We want the monitor-memory script to be executable without entering a password with root privileges.

To do this, we can edit the sudoers file:

ALL ALL=(ALL) NOPASSWD: /usr/local/bin/monitor-memory

Adding Memory Bandwidth Segment to Tmux Powerline

Now we can add a segment to the tmux powerline to display memory bandwidth.

We add a new segment script to ~/.config/tmux-powerline/segments/memory_bandwidth.sh:

#!/usr/bin/env bash
# memory_bandwidth.sh - Tmux-powerline segment for memory bandwidth monitoring using Intel PCM

# Source tmux-powerline lib functions
TMUX_POWERLINE_DIR_LIB="$HOME/.tmux/plugins/tmux-powerline/lib"

source "${TMUX_POWERLINE_DIR_LIB}/tmux_adapter.sh"

TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_SCRIPT_DEFAULT="/usr/local/bin/monitor-memory"

generate_segmentrc() {
    read -d '' rccontents  << EORC
# Memory bandwidth segment for tmux-powerline using Intel PCM

# Path to the monitor-memory script
export TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_SCRIPT="${TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_
SCRIPT_DEFAULT}"
EORC
    echo "${rccontents}"
}

__process_settings() {
    if [[ -z "$TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_SCRIPT" ]]; then
        export TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_SCRIPT="${TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_
MONITOR_SCRIPT_DEFAULT}"
    fi
}

run_segment() {
    __process_settings

    # Check if monitor script exists and is executable
    if [[ ! -x "$TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_SCRIPT" ]]; then
        echo "123"
        return
    fi

    # Get bandwidth data
    local bandwidth_data
    bandwidth_data=$(sudo $TMUX_POWERLINE_SEG_MEMORY_BANDWIDTH_MONITOR_SCRIPT 2>/dev/null)
    local exit_code=$?

    if [[ $exit_code -ne 0 || -z "$bandwidth_data" ]]; then
        return
    fi

    # Now split the line by commas and extract the last 3 fields
    local data_line=$(echo "$bandwidth_data" | tail -n 1)
    IFS=',' read -r -a fields <<< "$data_line"

    # Get total number of fields
    local num_fields=${#fields[@]}

    # Extract last three values
    local read_bw=$(echo "${fields[$((num_fields-3))]}" | xargs)
    local write_bw=$(echo "${fields[$((num_fields-2))]}" | xargs)
    local total_bw=$(echo "${fields[$((num_fields-1))]}" | xargs)

    content="📜 R ${read_bw} W ${write_bw}"

    echo "${content}"
    return 0
}

# Check if this script is being sourced or executed directly
if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
    # Being executed directly, run the segment
    run_segment
fi

setting the permissions to allow execution and we can test the output:

$ ./memory-bandwidth.sh
📜 R 481.66 W 587.30

and we are ready to add it to the tmux powerline.

Adding to Tmux Powerline Configuration

Now, modifying the configuration of tmux powerline ~/.config/tmux-powerline/themes/default.sh to include the new segment:

if [ -z "$TMUX_POWERLINE_LEFT_STATUS_SEGMENTS" ]; then
    TMUX_POWERLINE_LEFT_STATUS_SEGMENTS=(
        "tmux_session_info 148 234"
        "hostname 33 0"
        # ...
        "memory-bandwidth 90 255"   # Add memory bandwidth segment anywhere you like!
        # ...

        "vcs_others 245 0"
    )
fi

Of course you can adjust the colors to your favorite ones.

Notes

Simple and quick, we are done! Setting up more monitors makes the tmux powerline more informative and useful.

Disclaimer: This post is only for fun and testing purpose. Part of the code examples and the text in this post are generated by Claude 4.