Date: Tue, 28 Feb 2012 08:22:51 -0700 From: Scott Long <scottl@samsco.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: revisiting tunables under Safe Mode menu option Message-ID: <22F18CA9-4C58-446D-892B-28B67E343CE2@samsco.org> In-Reply-To: <201202280844.22142.jhb@freebsd.org> References: <4F26CC5A.2070501@FreeBSD.org> <4F4B5ED3.5090508@FreeBSD.org> <65B1891F-9079-4948-BF37-8A50B4E85071@samsco.org> <201202280844.22142.jhb@freebsd.org>
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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. Scotthelp
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