Igor Giamoniano

Posted on Mar 15

Diagnosing Multiple GPUs on Linux: How to Detect and Monitor Integrated and Dedicated GPUs

#linux #tutorial #opensource #showdev

If you run Linux on a system with both an integrated GPU and a dedicated GPU, you may have noticed something strange: some monitoring tools only show one GPU.

This situation is common on:

laptops with hybrid graphics
desktops with iGPU + dedicated GPU
systems using different driver stacks

For example, a monitoring tool like btop might show your AMD integrated GPU but completely ignore your NVIDIA card.

In this article we will walk through how to:

detect all GPUs installed in your system
verify that the correct drivers are loaded
identify which GPU is rendering your desktop
monitor usage for each GPU
automate the entire diagnostic process with a small script

Why This Happens

Linux systems with multiple GPUs may behave differently depending on:

installed drivers (open source vs proprietary)
kernel configuration
which GPU is configured as the primary renderer
monitoring tool capabilities

Example setup used in this article:

AMD Vega (integrated) — Ryzen 5 5600G
NVIDIA GTX 1050 Ti (dedicated)

In this configuration, btop showed only the AMD GPU while the NVIDIA card remained invisible in the default monitoring view.

Step 1 — Check if Both GPUs Are Detected

1.1 List GPUs via PCI

Run:

lspci | grep -i vga

Example output:

01:00.0 VGA compatible controller: NVIDIA Corporation GP107 [GeForce GTX 1050 Ti]
09:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cezanne [Radeon Vega Series]

If two entries appear, your hardware is being detected correctly.

1.2 Check Loaded Drivers

Run:

lsmod | grep -E 'nvidia|amdgpu|radeon'

Typical modules:

GPU	Kernel Module
NVIDIA	`nvidia`, `nvidia_drm`, `nvidia_modeset`
AMD (modern)	`amdgpu`
AMD (legacy)	`radeon`

If the modules appear, the drivers are loaded by the kernel.

1.3 Check Which GPU Is Rendering Your Desktop

Use:

glxinfo | grep "OpenGL renderer"

Example output:

OpenGL renderer string: NVIDIA GeForce GTX 1050 Ti

If glxinfo is missing, install it.

Ubuntu / Debian:

sudo apt install mesa-utils

Arch Linux:

sudo pacman -S mesa-utils

This command reveals which GPU is rendering the graphical session.

In hybrid setups, the integrated GPU often renders the desktop while the dedicated GPU activates only for demanding workloads.

Step 2 — Monitoring Each GPU

2.1 Integrated GPU (AMD / Intel) — Using btop

Launch:

btop

Inside btop:

press g to toggle GPU views
press 5 / 6 / 7 for specific GPU panels
configure via F2 → Options → CPU box → Show GPU info

2.2 NVIDIA Dedicated GPU — Using nvidia-smi

For NVIDIA GPUs the official tool is the most reliable:

watch -n 1 nvidia-smi

This updates every second and displays:

GPU utilization
memory usage
running processes

Structured output:

nvidia-smi --query-gpu=name,memory.used,memory.total,utilization.gpu --format=csv -l 1

Step 3 — Automating GPU Diagnostics

Create a script called:

check_gpus.sh

Script:

#!/bin/bash

echo "=== GPUs Detected ==="
lspci | grep -E "VGA|3D"

echo -e "\n=== Loaded Drivers ==="
lsmod | grep -E "nvidia|amdgpu|radeon"

echo -e "\n=== NVIDIA GPU ==="
nvidia-smi --query-gpu=name,memory.total --format=csv 2>/dev/null || echo "NVIDIA not detected"

echo -e "\n=== Rendering GPU ==="
glxinfo | grep "OpenGL renderer" 2>/dev/null || echo "glxinfo not available"

echo -e "\n=== DRM Devices ==="
ls /sys/class/drm | grep card

Make executable:

chmod +x check_gpus.sh

Run:

./check_gpus.sh

This quickly shows:

detected GPUs
active drivers
rendering GPU
NVIDIA status
DRM device nodes

Recommended Tools Summary

GPU Type	Recommended Tool	Command
AMD / Intel (integrated)	`btop`	`btop`
NVIDIA (dedicated)	`nvidia-smi`	`watch -n 1 nvidia-smi`
Hardware detection	`lspci`	`lspci \| grep -i vga`
Rendering check	`glxinfo`	`glxinfo \| grep "OpenGL renderer"`