Kernel Optimization Quirks
 

Hello all.

Before I begin, here is a little info on my system that may prove useful. I'm using Slackware 9 with Dropline GNOME 2.2.4 and XFree86 4.3 on an 800Mhz AMD Duron with an elderly 16MB nVidia RivaTNT video card.

And now for the dillema...

I recently compiled kernel 2.4.21 on my Slackware 9 installation. I had previously been using the precompiled bare.i kernel from the installation CD, and wanted to start using a kernel optimized for my processor. I followed the steps from the thread at the top of this forum to compile the new kernel, setting the CPU family to "Athlon/Duron/K7" and changing other settings relevant to my hardware.

The kernel installation ran and finished smoothly, and I was able to boot and use Dropline GNOME and all the apps I had previously compiled without problem.

Now here's the quirk: though the kernel is now technically optimized for my hardware, I've actually noticed a drop in performance. This is especially noticeable when X redraws the desktop after closing apps or windows. The performance degredation isn't monumental, not by any means, but it's still dissappointing since I had hoped to gain a little from it.

One thought has crossed my mind. Though everything still runs, the apps are nolonger optimized for my architecture. I read up on the Dropline documentation, which said that all their packages are optimized for i686, which, they say, includes the Athlon/Duron family.

So I'm stumped. If their software is still "theoretically" optimized for my CPU, then why the drop in performance? Am I correct in my assumptions, or is this as simple as an option I forgot to turn on in the kernel's menuconfig?

Thanks in advance.

If there is a drop, its probobly because you changed a setting in the kernel config that you shouldnt have.

Without knowing every setting you changed, we can't help you.

I dont think it was the processor optimization setting that made things slower, that would make no sense.


The other option is that its psychological. With all these "little" speed changes, it might just be your imagination. :)

Probably disabled some of the advanced
features required by your graphics card,
like for instance forgot to enable MTRR's? :)
agpgart, DRI, ...

Cheers,
Tink

Thanks for the advice, guys. I have since gone back to the kernel's menuconfig and checked for the advanced AGP and DRI options. To my surprise, they were all already selected.

I figured out that the kernel is in fact faster than the bare.i, except when redrawing the desktop. I suppose the next thing I'll try is compiling nVidia's drivers for my card (I'm currently using the generic nv drivers with XFree86.

Thanks for the help.

Did you check the MTRR's, too?
They are CRUCIAL! :}

Cheers,
Tink

Update:

I compiled the kernel again, this time with all the aforementioned options turned on (it took me a while to find all of them in the menuconfig).

The X redraw lag is gone and the kernel purs like a kitten.

Success!

Thanks for all your help, guys.