Re: Native preemption is the culprit [was Re: today's CURRENT lockups]

From: John Baldwin <jhb_at_FreeBSD.org>
Date: Fri, 9 Jul 2004 15:31:14 -0400
On Friday 09 July 2004 02:12 pm, Jon Noack wrote:
> On 07/09/04 13:06, Steve Kargl wrote:
> > On Fri, Jul 09, 2004 at 12:53:53PM -0500, Jon Noack wrote:
> >> On 07/09/04 12:25, Steve Kargl wrote:
> >>> On Fri, Jul 09, 2004 at 12:19:09PM -0500, Jon Noack wrote:
> >>>> On 07/09/04 12:15, John Baldwin wrote:
> >>>>> My test machine is not a true SMP machine either, just HTT.
> >>>>> It has been running a -j 256 worldloop overnight with no
> >>>>> problems, so I committed a slightly modified version of the
> >>>>> patch yesterday.
> >>>>
> >>>> Did you test with a UP kernel?  After your latest commit I have
> >>>>  been experiencing regular hard locks on my pre-HTT P4 machine.
> >>>>  Backing out rev. 1.114 of sched_ule.c fixes it.  See my
> >>>> previous message (Re: FreeBSD keeps hanging......):
> >>>> http://docs.freebsd.org/cgi/mid.cgi?40EECC49.3070501
> >>>
> >>> I've tested it on a UP kernel (HTT enabled, ACPI disabled, APIC
> >>> enabled, ULE).   Appears to work fine.
> >>
> >> Perhaps it's just extraneous information, but if it's really a UP
> >> kernel (as in, no 'options SMP') then whether you have HTT enabled
> >> doesn't matter at all -- the kernel won't use it.
> >
> > Yes, I know. :-)  I'm just reporting what dmesg tells me about the
> > CPU.
> >
> > CPU: Mobile Intel(R) Pentium(R) 4 - M CPU 2.00GHz (1994.12-MHz
> > 686-class CPU) Origin = "GenuineIntel"  Id = 0xf27  Stepping = 7
> > Features=0xbfebf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,C
> >MOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>
> Mine also lists HTT, but doesn't actually support it:
> CPU: Intel(R) Pentium(R) 4 CPU 2.53GHz (2539.10-MHz 686-class CPU)
>    Origin = "GenuineIntel"  Id = 0xf24  Stepping = 4
>
> Features=0x3febfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MC
>A,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM>
>
> I remember a discussion about this a long time ago, but don't remember
> the details.  Regardless, the flag doesn't actually mean the processor
> supports HTT.

The flag means you can ask the CPU how many cores it has, but it may reply 
with "I have 1 core."  If there is more than 1 core, then we print out a 
second line saying how many cores there are on each CPU.

-- 
John Baldwin <jhb_at_FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org
Received on Fri Jul 09 2004 - 17:30:05 UTC

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