[LinuxBIOS] Help with meaning of config options.

[Steve Isaacs]

When I look at the options passed to the compiler on the command line I
see the following:

-DCONFIG_MAX_CPUS='4' -DCONFIG_MAX_PHYSICAL_CPUS='2'
-DCONFIG_LOGICAL_CPUS='1'

Can someone help me understand what the difference between these is? I'm
working with two dual core opterons and this doesn't seem right to me.

Steve

[Marc Jones]

Steve Isaacs wrote:
> When I look at the options passed to the compiler on the command line I
> see the following:
>
> -DCONFIG_MAX_CPUS='4' -DCONFIG_MAX_PHYSICAL_CPUS='2'
> -DCONFIG_LOGICAL_CPUS='1'
>
> Can someone help me understand what the difference between these is? I'm
> working with two dual core opterons and this doesn't seem right to me.
>
> Steve

CONFIG_MAX_CPUS :  Saves space in the ACPI tables and additional stack 
space for maximum possible number of cores in the system. Might be 
better named as CONFIG_MAX_CPUs_CORES (AMD only)

CONFIG_MAX_PHYSICAL_CPUS: Used to set memory SPD addresses and in 
coherent HyperTransport initialization (AMD only)

CONFIG_LOGICAL_CPUS : This is the flag to build in multi-core support. 
Similar to CONFIG_MAX_CPUS but only set to 0 or 1. (Used by AMD and 
Intel code)

Your setup:
CONFIG_MAX_CPUS : 4  - 4 cores
CONFIG_MAX_PHYSICAL_CPUS: 2 - 2 CPUs
CONFIG_LOGICAL_CPUS : 1 - build multi core support in.

Marc

[Steve Isaacs]

Thanks.

On Tue, 2007-12-04 at 10:18 -0700, Marc Jones wrote:
>
> CONFIG_MAX_CPUS :  Saves space in the ACPI tables and additional stack 
> space for maximum possible number of cores in the system. Might be 
> better named as CONFIG_MAX_CPUs_CORES (AMD only)
>
> CONFIG_MAX_PHYSICAL_CPUS: Used to set memory SPD addresses and in 
> coherent HyperTransport initialization (AMD only)
>
> CONFIG_LOGICAL_CPUS : This is the flag to build in multi-core support. 
> Similar to CONFIG_MAX_CPUS but only set to 0 or 1. (Used by AMD and 
> Intel code)
>
> Your setup:
> CONFIG_MAX_CPUS : 4  - 4 cores
> CONFIG_MAX_PHYSICAL_CPUS: 2 - 2 CPUs
> CONFIG_LOGICAL_CPUS : 1 - build multi core support in.

I'm not suggesting a change. I'm just trying to make sure I understand
the semantics.

So, would it make sense to think of it as having an option that defines
the number of cores per CPU (e.g. CONFIG_CORES_PER_CPU) and let
CONFIG_MAX_CPUS equal CONFIG_MAX_PHYSICAL_CPUS * CONFIG_CORES_PER_CPU?

Steve

[Marc Jones]

Steve Isaacs wrote:
> Thanks.
>
> On Tue, 2007-12-04 at 10:18 -0700, Marc Jones wrote:
> > CONFIG_MAX_CPUS :  Saves space in the ACPI tables and additional stack 
> > space for maximum possible number of cores in the system. Might be 
> > better named as CONFIG_MAX_CPUs_CORES (AMD only)
> >
> > CONFIG_MAX_PHYSICAL_CPUS: Used to set memory SPD addresses and in 
> > coherent HyperTransport initialization (AMD only)
> >
> > CONFIG_LOGICAL_CPUS : This is the flag to build in multi-core support. 
> > Similar to CONFIG_MAX_CPUS but only set to 0 or 1. (Used by AMD and 
> > Intel code)
> >
> > Your setup:
> > CONFIG_MAX_CPUS : 4  - 4 cores
> > CONFIG_MAX_PHYSICAL_CPUS: 2 - 2 CPUs
> > CONFIG_LOGICAL_CPUS : 1 - build multi core support in.
>
> I'm not suggesting a change. I'm just trying to make sure I understand
> the semantics.
>
> So, would it make sense to think of it as having an option that defines
> the number of cores per CPU (e.g. CONFIG_CORES_PER_CPU) and let
> CONFIG_MAX_CPUS equal CONFIG_MAX_PHYSICAL_CPUS * CONFIG_CORES_PER_CPU?
>
> Steve

I would ack that patch.
Marc