when to use Linux SMP kernel?

[Anthony_141]

We have ML350 G5 with a single Dual-Core Xeon processor.

We loaded Redhat ES 4 and on bootup, it defaults to the SMP version of the kernel.

With one processor (though it is dual-core), should we be using the SMP or non-SMP kernel?

How would we know this ourselves - is there a good document explaining this anywhere?

What advantage (if any) would the SMP kernel give us, or would it depend on what applications we were running?

[Florian Heigl (new acc)]

You need an SMP kernel.

SMP means symmetric multiprocessing, as in 'multiple cpus are doing Your work'. A dual core cpu is essentially two cpus in the packaging of one, so You need to run an smp kernel.

[Ivan Ferreira]

Use it if you have more than one cpu or hyperthreading enabled in the BIOS.

[Anthony_141]

Can anyone then expain if you can have hyperthreading enabled, under what circumstances would you disable it?

[Stuart Browne]

Some older applications and hardware get confused about what Hyper-threading is.

If it's modern (i.e. last 5-6 years or so), then you turn it on, and never think about it again.

With RHEL4 and a G5 series server, turn it on and leave it on.

[Anthony_141]

non issue for us now as we are going to purchase different servers than the G5 (last we heard anyway)