Monitor guest activity using the agent

[afbjorklund]

Description

I am looking for a feature, where I can see the CPU usage and RAM usage of an instance. Preferrably disk usage too, if possible.

However, I could not find this to be easilly accessible in QEMU the same way that it is in VirtualBox or Docker or what have you ?

One workaround that I was considering earlier, would be to run a small program in the guest to output such information.

It would not be as accurate ("inside") as quering the hypervisor ("outside"), but it would be "good enough" for my purposes.

---

I made a proof-of-concept, using gopsutil. What you do you think about the idea ?

package main

import (
	"fmt"
	"path/filepath"
	"time"

	"github.com/shirou/gopsutil/v3/cpu"
	"github.com/shirou/gopsutil/v3/disk"
	"github.com/shirou/gopsutil/v3/host"
	"github.com/shirou/gopsutil/v3/mem"
)

func main() {
	_, _ = cpu.Percent(1*time.Second, true)
	h, _ := host.Info()
	p, _ := disk.Partitions(false)

	fmt.Printf("Host: %v\n", h.Hostname)

	mountpoint := "/"
	for _, part := range p {
		device, err := filepath.EvalSymlinks(part.Device)
		if err != nil {
			continue
		}
		if part.Fstype == "squashfs" { // skip /snap
			continue
		}
		fmt.Printf("%s %s\n", device, part.Mountpoint)
		if device == "/dev/vda1" {
			mountpoint = part.Mountpoint
		}
	}

	for {
		t := time.Now()
		c, _ := cpu.Percent(0, false)
		v, _ := mem.VirtualMemory()
		d, _ := disk.Usage(mountpoint)

		fmt.Printf("%v\n", t.Format(time.RFC3339Nano))
		fmt.Printf("Cpu: %.2f%%\n", c[0])
		fmt.Printf("Mem: %.2f%%\n", v.UsedPercent)
		fmt.Printf("Disk: %.2f%%\n", d.UsedPercent)

		time.Sleep(1 * time.Second)
	}
}

Probably would use JSON lines, rather than text. So that it can be parsed, and graphed, on the lima client side.

• https://github.com/afbjorklund/lima-gui/issues/11

[afbjorklund]

The main reason to have this running in the agent, is that the cpu counters need to keep state from last time...

Otherwise there is a pause (it is 1 second in the above program), where it accumulates enough relative values.

[AkihiroSuda]

Will this be used for GUI dashboard or something similar?

[afbjorklund]

Will this be used for GUI dashboard or something similar?

That was the idea, but I guess you could view it in the console too

Something similar to the output you can get from e.g. lima vmstat 1

(Another workaround would be to run top, over the lima connection.)

But the main idea was for some graphs, like in https://virt-manager.org/

---

I think I will move the "host" info to a separate feature, from this one.

It grew a bit, from the original idea of just parsing /etc/os-release

[afbjorklund]

We used a command-line tool similar to this feature, for benchmarking minikube:

https://github.com/tstromberg/cstat

It was featured in one of the talks, on how to make Kubernetes start up faster:

https://kccnceu20.sched.com/event/Zerq/improving-the-performance-of-your-kubernetes-cluster-priya-wadhwa-google