Comments on: Tuning the Linux Kernel’s Completely Fair Scheduler

By: Bill Anderson

Bill Anderson — Tue, 18 Oct 2011 12:23:54 +0000

The answer to this questions depends on the version of the kernel that you are using. CFS has undergone many changes since its introduction into the kernel. It seems to me that writing a script is easier, and less dependent on the kernel version. You need to remember that the priority displayed with the ps command is not the actual kernel priority value for the process. Also, the priority of a process is a dynamic value, and ps only reflects a snapshot in time. The kernel no longer uses the traditional priority ques. As soon as I complete another project, I will update this article.

By: Bill Anderson

Bill Anderson — Tue, 18 Oct 2011 12:08:53 +0000

This is an interesting question. Without doing a bit of research, I cannot think of the data structure that tracks user logins. I would use a tool like cscope or cs to search the source code for the functions that you need.

By: Ramoza

Ramoza — Mon, 03 Oct 2011 06:09:02 +0000

Is there any method to get user id within the code of fair schedular i.e. sched.c or sched_fair.c file. i want to check whether administrator has logged onto the system or some other user.

By: Man3

Man3 — Thu, 22 Sep 2011 23:21:02 +0000

Hi, I need to modify the linux kernel scheduler so that a particular process(with a special name) gets the highest priority always. Please guide me where to look for the changes to be made. I am very new to the kernel development.

Thanks.

By: Bill Anderson

Bill Anderson — Thu, 02 Sep 2010 19:42:32 +0000

You can find the instructions in the Documentation/scheduler/sched-design-CFS.txt file in the Linux source tree.

By: Bill Anderson

Bill Anderson — Thu, 02 Sep 2010 19:32:18 +0000

I checked the source for 2.6.32-24 and that CONFIG_KERNEL_DEBUG is now CONFIG_DEBUG_KERNEL and CONFIG_SCHED_DEBUG still does exist. Name changes between version is not uncommon. It makes working with the kernel more exciting.

By: anonyomus

anonyomus — Wed, 18 Aug 2010 13:34:56 +0000

Does anyone know how to create the directory /dev/cpuctl and set a certain process to be scheduled in such a way. My interest is decreasing the performance of the kvm processe on my notebook that runs the Windows XP guest. It eats far too much CPU especially when it is used only Lotus Notes.

By: anonyomus

anonyomus — Wed, 18 Aug 2010 13:28:04 +0000

but the second portion of your post does work for Ubuntu 10.04 /boot/config-2.6.32-22-generic:
# fgrep CONFIG_PREEMPT /boot/config-$(uname -r)
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set

By: anonyomus

anonyomus — Wed, 18 Aug 2010 13:26:26 +0000

fgrep CONFIG_KERNEL_DEBUG /boot/config-$(uname -r)
Works in Ubuntu but won’t return anything because the string is unusued.
fgrep CONFIG_SCHED_DEBUG /boot/config_$(uname -r)
Certainly won’t work in Ubuntu

By: Bill Anderson

Bill Anderson — Mon, 22 Mar 2010 11:11:14 +0000

You are correct. For those interested, the package is libcgroup1. I will provide more details on this package in a separate article.