RT Kernel compile and install help needed.

[Valdis.Kletnieks at vt.edu]

On Tue, 04 Nov 2014 13:07:47 +0530, Chanchal Paul said:

> I am fairly new to kernel compilation and installation process, still i
> managed to learn from Kernelnewbies and RT-wiki and managed to patch
> 3.12.14 vanilla kernel with rt patch 3.14.12.

You *really* want to get the correct patch on the kernel release. Mixing
and matching a 3.12 kernel and a 3.14 patch will almost certainly lead to
weird results.

> Now my confusion arises when i see my uname -a string as "Linux
> paul-lubuntu 3.14.12-rt9 #2 SMP PREEMPT Tue Oct 28 13:30:27 UTC 2014 x86_64
> x86_64 x86_64 GNU/Linux" which indicated that i have a preemptive kernel
> installed. but the c program from "
> https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO" for "Runtime
> detection of an RT-PREEMPT Kernel" only prints "this is a vanilla kernel".
> So, my question is am I running a vanilla kernel or a real-time kernel? If
> I am not then what are the steps to properly install a real-time kernel?

After applying the patch, you need to run 'make menuconfig' or similar
and actually enable the hard realtime support.

Also, be aware that most of the -rt patch has over the years been upstreamed,
so for the vast majority of uses, applying the patch isn't really worth
it - 95% of the people using that patch don't get any measurable benefit.

(Yes, most of the people using it *claim* they get "better latency response"
from their desktop.  And most of them are having total placebo effect. They
think they should get better response, so they think they get it.  Nobody's
actually done a blind study, where grub randomly boots one kernel or another
and the user doesn't know which, and measured any difference that way....)
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