Date: Wed, 22 May 2002 09:58:33 -0700 (PDT) From: "Dorr H. Clark" <dclark@applmath.scu.edu> To: Alfred Perlstein <bright@mu.org> Cc: freebsd-smp@FreeBSD.ORG Subject: hyperthreading: myth or legend? (was Re: hyperthreading? (was Re: question)) Message-ID: <Pine.GHP.4.21.0205220940410.28331-100000@hpux38.dc.engr.scu.edu> In-Reply-To: <20020514222840.GB1585@elvis.mu.org>
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On Tue, 14 May 2002, Alfred Perlstein wrote: > * Dorr H. Clark <dclark@applmath.scu.edu> [020514 10:21] wrote: > > > > On Fri, 10 May 2002, Alfred Perlstein wrote: > > > > > * David <david_929@hotmail.com> [020510 18:08] wrote: > > > > > > > > Hi just wanna know if newest FreeBSD supports > > > > Dual P4-Xeon? > > > > > > Yes, even "hyperthreading" is supported. > > > > Is this really true? I thought it was only getting > > as far as putting out some misleading boot messages. > > It sure looked like it was working on the machine I was playing with. > Could you be more specific? I don't have access to a fancy Xeon, I just have a PIII dual-banger, so I'm relying on the list traffic. To summarize the past two months: On Thu, 14 Mar 2002, John Baldwin wrote: > On 14-Mar-2002 Steve Wingate wrote: > > Has anyone testing Intel Xeon hyperthreading on FreeBSD? I'm building > > a Dual Xeon box and I was curious if FreeBSD would see that as > > two processors or four. TIA. > We currently don't support hyperthreading in FreeBSD. > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ On Thu, 14 Mar 2002, Terry Lambert wrote: > Kenneth Culver wrote: > > I don't know if anyone is working on that, but from what I could tell, > > in a lot of cases, enabling the hyperthreading actually *decreased* > > performance of a lot of multithreaded and single threaded apps. > It requires extensive compiler support. > If you read the Intel documentation on how to write a compiler > that does the right things, it reads like a list of sixteen > "don't do this thing GCC did, do this instead". > So the answer is really a question... does the original poster > have their patches to GCC ready so that we can compile code > that tests hyperthreading? On Tue, 23 Apr 2002, FiberOps wrote: > It only means His motherboard has the capability of holding quad cpus > > > > we have a nice SMP system here, a 2 x P4 2.2GHz Supermicro P4DP6 > > ^^^^^^^^^^^^^ > > > FreeBSD/SMP: Multiprocessor motherboard > > > cpu0 (BSP): apic id: 0, version: 0x00050014, at 0xfee00000 > > > cpu1 (AP): apic id: 6, version: 0x00050014, at 0xfee00000 > > > cpu2 (AP): apic id: 1, version: 0x00050014, at 0xfee00000 > > > cpu3 (AP): apic id: 7, version: 0x00050014, at 0xfee00000 > > cpu[0-3], that's 4 processors. Does this mean that FreeBSD can > > actually handle the hyperthreading in the latest Xeons and recognizes > > one P4 processor as 2 in an SMP environment? On Tue, 23 Apr 2002, John Baldwin wrote: On 23-Apr-2002 FiberOps wrote: > > Nevermind my answer, I thought the P4DP6 was the P4QH6 > > which is quad . Your thoughts about the hyperthreading seem > > to be correct unless He was mistaken about the motherboard. > That is actual probed CPU's, not slots, so it looks like we at > least see them properly. I'm curious if we IPI them properly > since we currently abuse physical ID's for addressing APIC's > rather than using logical ID's like we should. Do all 4 CPU's > launch ok at the bottom of the boot messages? > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ This final message was not followed up except by me, although someone else informed me that while the CPUs launch, FreeBSD can't run processes on them. So I thought I'd try to stir up an answer to the original question: For the latest Xeon motherboards, does FreeBSD 4.x stable support hyperthreading? If not, does the current TOT? If not, why not? Is gcc an issue or not? If gcc is an issue, would this be an obstacle for all gcc-based OSes, not just FreeBSD, most prominently among these Linux? Clear answers gratefully appreciated, =dhc To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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