[LAU] Kernel 2.6.39

[Robin Gareus]

On 06/21/2011 09:03 PM, Ralf Mardorf wrote:
> Hi,
> 
> could there be any disadvantages for averaged desktop users, server
> usage etc., if the kernel 2.6.39 is build as PREEMPT kernel?
> 
> Today I installed the kernel from the repositories of a major Distro:
> 
> $ uname -a
> Linux debian 2.6.39-2-amd64 #1 SMP Wed Jun 8 11:01:04 UTC 2011 x86_64
> GNU/Linux
> 
> Some time ago I build the kernel myself:
> 
> $ uname -a
> Linux debian 2.6.39.1 #1 SMP PREEMPT Tue Jun 7 01:40:05 CEST 2011 x86_64
> GNU/Linux
> 
> I'm asking, because I want to know, if it would be reasonable to appeal,
> that major distros should build it as PREEMPT kernel.

Well, they should offer the option (a kernel-flavor - compare to -bigmem
or -xen, or -vserver, etc). but as default: no.

Preemptive scheduling introduces some overhead [for each process] and
effectively reduces throughput.

As the vast majority of systems (both Desktop and Server) do not run any
processes with SCHED_FF or use elevated scheduling priorities. Thus
there is no benefit and only drawbacks (the machine is a tiny-bit slower
and consumes more power with a PREEMPT kernel).

robin