Date: Fri, 16 Jun 2006 15:09:28 -0400 From: John Baldwin <jhb@freebsd.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-current@freebsd.org, Nate Lawson <nate@root.org> Subject: Re: Freeze due to performance_cx_lowest=LOW Message-ID: <200606161509.28998.jhb@freebsd.org> In-Reply-To: <44929864.4080207@icyb.net.ua> References: <1148837064.00534930.1148826605@10.7.7.3> <200606011504.31635.jhb@freebsd.org> <44929864.4080207@icyb.net.ua>
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On Friday 16 June 2006 07:39, Andriy Gapon wrote: > on 01/06/2006 22:04 John Baldwin said the following: > > On Tuesday 30 May 2006 23:19, Nate Lawson wrote: > >> Andriy Gapon wrote: > >>> on 29/05/2006 23:10 Nate Lawson said the following: > >>>> disable apic (hint.apic.0.disabled="1"). I isolated this a little while > >>>> ago to the change to enable LAPIC timer. However, there is currently no > >>>> easy way to disable the LAPIC timer with APIC enabled so you have to > >>>> disable APIC. jhb@ and I have been discussing how to do this better but > >>>> no easy answers apparently. > >>> I am not sure what I am talking about, but is it potentially possible to > >>> drive timer system by more than one clock, actively using the most > >>> precise of them at any particular moment ? So that if LAPIC timer stops > >>> i8254 can be used instead. > >> That requires mixed mode delivery -- i8254 on legacy PIC irq and APIC > >> mode for other interrupts. jhb@ just killed this and isn't eager to add > >> it back. I'll let him explain if he has more to add. > > > > Namely that it is unreliable and expressly forbidden by the ACPI spec. > > > > Maybe I will say something too ignorant for this list, but is it > possible to drive hardclock with two interrupts (I haven't thought yet > how, though) and use RTC as the second interrupt source ? > I think that RTC/IRQ8 (usually) doesn't have problems associated with > 8254 timer/IRQ0 and can be used without mixed mode. Well, you could use the RTC instead of the lapic timer on CPU 0 and then use IPIs to forward clock interrupts to all the other CPUs just as we did before we used the lapic timer. -- John Baldwin
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