Limiting CPU Usage of A Process in CentOS/RHEL 7

In HPC, we may need to protect head node from unnecessary heavy process that may cause login problem for users. One of the solutions is by using cpulimit. We can create a cronjob to monitor all processes and set certain limit for them. This is how I usually did in CentOS/RHEL 7.x.

  1. Install cpulimit package from EPEL repo.

yum install cpulimit

  1. Create a script to monitor the process. The script below is a modified version of the script in this forum. You can modify inputs of the first 3 variables: CPU_LIMIT, BLACK_PROCESSES_LIST, and WHITE_PROCESSES_LIST.

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got stuck at “Wait for Plymouth Boot Screen to Quit”

If you can’t get to the login page (booting gets stuck at “Wait for Plymouth Boot Screen to Quit”) after CUDA driver installation, then it’s probably because the kernel is trying to load xorg.conf created by NVIDIA driver. I got this experience in my laptop that has Intel + NVIDIA GPUs running CentOS 7.

Workaround Solution: Continue reading

error: “Oh no! Something has gone wrong.”


If the above message suddenly comes up in your screen after CUDA driver installation in RedHat/CentOS/Fedora OS, don’t be panic. This is happened because of xorg-x11-drv-nvidia-gl package, which is part of cuda-drivers dependencies. I got this experience in my laptop that has Intel + NVIDIA GPUs. I guess it’s because the Intel GPU is the primary GPU in my laptop, and for RedHat/CentOS/Fedora there’s no a kind of official Optimus technology, like in Windows.

Workaround Solution: Continue reading

Optimus + CUDA in Fedora 20

Recent laptops mostly come with hybrid-graphics system (two GPUs in one machine: an integrated GPU and a discrete GPU). It was first designed to control power consumption in laptops. By default, the operating system will use the integrated GPU which is less power consumption. Only when heavy activities (gaming, graphic rendering, GPU computing, etc) are performed, then operating system will move the workload to the discrete GPU.

For laptop with NVIDIA GPU, there is NVIDIA Optimus Technology for auto-switching between integrated GPU and discrete GPU. Unfortunately, NVIDIA support for this technology in Linux is not as good as in Windows. Since discrete GPU is a secondary card, installing the driver for NVIDIA GPU is not easy and may cause problem with the display manager in Linux. Continue reading