kernel and kernel-smp?

[Sam Varshavchik]

Jesse Hannah writes:

> What is the difference between the regular kernel and kernel-smp? For
> example, my grub.conf looks something like:

Kernel-smp is the kernel for systems with more than one CPU.

"kernel" will boot on a system with two or more CPUs, but only one CPU will 
be in use.

"kernel-smp" is required to use more than one CPU.

On certain systems, "kernel-smp" may be required even if there's only one 
CPU.  Some high-end boards may actually have some hardware that's only 
supported by the kernel-smp kernel.

You will also need to use "kernel-smp" with Pentium 4, in order to use 
hyperthreading (which is more accurately described as “hyperventilating”), 
which essentially looks like a second CPU to Linux.

"kernel" should also boot on a P4, but you'll be running without 
hyperventilating.

> title Windows XP
>     ...
> title Fedora Core (2.6.9-1.667-smp)
>     kernel /vmlinuz-2.6.9-1.667-smp ro root=LABEL=/1 rhgb quiet
>     initrd /initrd-2.6.9-1.667-smp.img
> title Fedora Core-up (2.6.9-1.667)
>     kernel /vmlinuz-2.6.9-1.667 ro root=LABEL=/1 rhgb quiet
>     initrd /initrd-2.6.9-1.667.img
> 
> Does it make any difference which one I use normally?

Well, theoretically you should have stuff running faster with kernel-smp. 
However, in some marginal cases the extra benefit gained from 
hyperventilating may not outweigh extra overhead of multi-CPU support.


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