Linux kernel optimisations question

Khannie

Just wondering if a 686 specific kernel will be much better than a 386 kernel?

Or a K7 specific one for AMD machines?

What kind of performance difference would you be looking at? Are those extra instructions all that good at the kernel level?

Thanks in advance.

L1011

Khannie wrote:

Just wondering if a 686 specific kernel will be much better than a 386 kernel?

Or a K7 specific one for AMD machines?

What kind of performance difference would you be looking at? Are those extra instructions all that good at the kernel level?

Thanks in advance.

Considering its basically no loss in compile time, its worth your while. 686 or higher optomisations should enable stuff like MMX optomised memcpy() support. K7 would let it use 3DNow!, which Intel's don't have, and so on

Just never use i486 except on an i486; gcc makes terrible i486 code that runs slower on Pentium and higher than i386 code does..

nadir

yeah, you should be able to alter the makefiles too if u want and add in whatever optomisations u want, or set em in bash. I'm not sure, play aruond with it, but yeah go for i686 for sure,

rsynnott

It won't make a dramatic difference, but it won't do any harm. One thing certainly worth compiling for your processor, tho, is mplayer. The version that comes with most distrobutions is very cautious of using SSE and so on, especially on a processor it doesn't know about (default mplayers tend to refuse to use most extensions on an AMD64).

Khannie

Ok, I'm starting to get it now.

Actual runtime differences will be determined by whether or not I've compiled specific applications to use the extra instructions. Ok, that makes sense. My original question was specific to just upgrading the kernel (there's an apt-get-able K7 kernel), and how that on its own would improve anything, but rsynnott answered that with "not much".

Thanks.

rsynnott

There are of course exceptions to the "not much". If you use kernel-space VPN and have a Via C3, for instance, it might certainly be of interest.