Re: RHEL4 running on VMWare ESX 2.5.2

[Eric Hagberg MorganStanley com]

On Wed, 26 Oct 2005, Tom Sightler wrote:

> Also, if you are attempting to use SMP virtual machines you might want
> to boot with the "noht" flag otherwise it seems that the kernel in RHEL4
> detects the two "virtual" cpu's as a single, ht cpu.

The noht flag doesn't do anything for RHEL4 kernels.

See /usr/src/linux/arch/i386/kernel/setup.c on an RHEL3 vs. an RHEL4
machine to see that it's gone.

And in that same file, there's an interesting note (under RHEL4):

                /*
                 * If the BIOS enumerates physical processors before logical,
                 * maxcpus=N at enumeration-time can be used to disable HT.
                 */
                else if (!memcmp(from, "maxcpus=", 8)) {
                        extern unsigned int maxcpus;

Bummer if your bios doesn't enumerate physical before logical procs, eh?
Or if you thought that "noht" flag actually disables hyperthreading under
RHEL4.