Re: revisiting tunables under Safe Mode menu option

From: John Baldwin <jhb_at_freebsd.org>
Date: Tue, 28 Feb 2012 08:44:22 -0500
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).

> > [dropped proposals snipped]
> >> o hw.eisa_slot - Looks like something from ancient times.  Probably just
> >> irrelevant for most systems.
> >> 
> 
> This turns off probes in the ISA ioport space that used to cause problems.  Why get rid of it?  Is its presence causing you problems?

I agree this should probably stay.

-- 
John Baldwin
Received on Tue Feb 28 2012 - 14:18:28 UTC

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