Plotting resource usage statistics

Using monitor to generate CPU and memory use statistics for a process and its children:

monitor -i 100 -o /tmp/usage.tsv ebk-select -n

Here I am using ebk-select with fzf as the selection command.

The Monitor output looks like this:

Read the data into Python using Pandas:

import pandas as pd
data = pd.read_table("/tmp/usage.tsv")

Convert the memory measurements from bytes to megabytes:

data["RSS"] /= 1024 * 1024
data["VMS"] /= 1024 * 1024

Set up a figure for Matplotlib to plot to, with two subplots: one for CPU usage and one for memory:

import matplotlib.pyplot as plt
plt.style.use("bmh")
fig = plt.figure(figsize=(6, 6), layout="constrained")
mem, cpu = fig.subplots(nrows=2, sharex=True)

For each process in the table, plot the CPU usage against time:

grouped = data.groupby("Command")

for cmd, subset in grouped:
    cpu.plot("Time", "CPU%", "o-", data=subset, label=cmd)

cpu.set_xlabel("Time, s")
cpu.set_ylabel("CPU, %")

Plot the memory usage (RSS or VMS) against time in the other subplot. Since we have a shared x-axis, we don’t set an x label this time.

for cmd, subset in grouped:
    mem.plot("Time", "RSS", "o-", data=subset, label=cmd)

mem.set_ylabel("RSS memory, MiB")
mem.set_ylim(0)

Add the legend to one of the subplots (whichever has the most white space):

cpu.legend()

Then save the figure to file:

fig.savefig("/tmp/usage.svg", transparent=True)

Here is the full script: plotting-monitor-output.py

[Package versions used: python 3.14.3, pandas 2.3.3, matplotlib 3.10.8]