Re: revisiting tunables under Safe Mode menu option

On Feb 28, 2012, at 6:44 AM, John Baldwin wrote:

> On Monday, February 27, 2012 2:03:21 pm Scott Long wrote:
>> 
>> On Feb 27, 2012, at 3:45 AM, Andriy Gapon wrote:
>> 
>>> on 30/01/2012 18:59 Andriy Gapon said the following:
>>>> 
>>>> First, I think that this proposal/discussion could have been more useful before
>>>> the 9.0.  Maybe the RE would be interested in adding another item to their
>>>> pre-release checklist: ask developers about what could be dropped and what should
>>>> be added to the Safe Mode settings in a new (.0) release.  Probably the developers
>>>> should keep the Safe Mode in mind too when adding new features or making other
>>>> drastic changes, but the reminder should be welcome.
>>> [snip]
>>>> o Since we have a separate ACPI option and because ACPI now is almost a mandatory
>>>> thing (and not a significant source of boot troubles), maybe we could remove the
>>>> code that automatically disables ACPI in Safe Mode?
>>>> 
>>>> o hint.apic.0.disabled - APIC code doesn't seem to be a significant source of boot
>>>> troubles, like ACPI it has become almost a mandatory thing.  So maybe we should
>>>> remove this setting?
>> 
>> Turning off the APIC turns off SMP in a very efficient, clean manner.  I added this not to isolate the APIC code, but to turn off SMP.  That's why 
> it's there, and I'd like the ability to turn off SMP to stay there in some form.  If there's a better way to disable SMP that doesn't get into 
> problems with interrupt delivery, then please propose it.  As for it being mandatory, it's really only mandatory for MSI these days, though it used 
> to be required for more complex PCIX topologies.
> 
> You want APIC for other things as well (hwpmc(4) requires it, as do CMCI
> interrupts, and we really do like to make use of the local APIC timer).
> 

Well, 'Safe Mode' isn't meant to be a normal, continuous operating mode, it's meant to be a debug mode that helps boot otherwise unbeatable systems.

Scott