halting HTT

[John Baldwin]

On 01-Dec-2003 Igor Sysoev wrote:
> I had noticed that on Nov 11, 2003 in src/sys/i386/i386/mp_machdep.c
> HTT CPUs are not halted by default.  What is the reason to do it ?
> Is it not better to allow logical CPUs to handle interrupts ?

HTT CPUs were halted by default because we needed them to always be
used to work around other bugs.  Since the other bugs are fixed, we
no longer need HTT CPUs unless the user wants them.  If you disable
HT in the BIOS for example, we no longer probe them.  Thus, it doesn't
make sense to halt the CPUs if the user has explicitly asked for
them.

> Besides if I try to halting logical CPUs by machdep.hlt_cpus=10 or
> machdep.hlt_logical_cpus=1 then computer is partially freezed, i.e
> top that running in ssh session could contunue to run but I can not
> login to computer anymore.
> 
> I'm using 5.1-CURRENT from 2003.11.28.00.00.00 and
> machdep.logical_cpus_mask=10

I do not know why your machine freezes when you halt the logical
CPUs.

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/