Messages in this thread | | | From | "Mark Cuss" <> | Subject | Re: Kernel reports 4 CPUS instead of 2... | Date | Wed, 16 Oct 2002 16:21:37 -0600 |
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It turns out that some part of Red Hat 8 was at fault.
I installed Red Hat 7.3 and compiled a custom 2.4.19 kernel.
Speaking of the previous compile test: The dual PIII 1 Gig box took 9.2s to compile my test block of code... The new Dual Xeon 2.2 now takes 4.26 s (with hyperthreading. Its about 1/2 a second slower without) - thats better than double. I'm not sure if its just the kernel that was running slower on Red Hat 8, or maybe gcc 3.2 is just a lot slower than 2.96...
Thanks to everyone for your help
Mark
----- Original Message ----- From: "Samuel Flory" <sflory@rackable.com> To: <mcuss@cdlsystems.com> Cc: <jamesclv@us.ibm.com>; <root@chaos.analogic.com>; <linux-kernel@vger.kernel.org> Sent: Wednesday, October 16, 2002 2:47 PM Subject: Re: Kernel reports 4 CPUS instead of 2...
> Mark Cuss wrote: > > >Speaking of performance.... :) > > > >Has anyone done any testing on a dual CPU configuration like this? I've > >been testing this box with both the RedHat 8 Stock Kernel (2.4.18.something) > >and 2.4.19 from kernel.org. Currently, I can't make the thing perform > >anywhere near as fast as my Dual PIII 1 Ghz box (running 2.4.7 for the last > >325 days...) . I've been compiling the same block of code on both the > >machines and comparing the times. The PIII box is around 7 s, while the new > >Xeon Box is 13 or 14s... > > > >My thinking was that since the CPUs are much faster, and the FSB is faster, > >and the disk controller is faster, that the computer would be faster. > > > >The hardware is obviously faster, I'm sure its just something I've done > >wrong in the kernel configuration... If anyone has any advice or words of > >wisdom, I'd really appreciate them... > > > > > > Try shutting off hyperthreading in the bios. Keep in mind > hyperthreading is net loss if you are running a single nonthreaded app. > Also you might want to check if there aren't io speed issues. > > A good way to see the effects positive effects of hyperthreading is a > kernel compile. A "make -j 4 bzImage" should be much much faster on the > Xeon system with hyperthreading than a P3. > > > > >Mark > > > >----- Original Message ----- > >From: "James Cleverdon" <jamesclv@us.ibm.com> > >To: <root@chaos.analogic.com>; "Samuel Flory" <sflory@rackable.com> > >Cc: "Mark Cuss" <mcuss@cdlsystems.com>; <linux-kernel@vger.kernel.org> > >Sent: Wednesday, October 16, 2002 1:28 PM > >Subject: Re: Kernel reports 4 CPUS instead of 2... > > > > > > > > > >>On Wednesday 16 October 2002 10:54 am, Richard B. Johnson wrote: > >> > >> > >>>On Wed, 16 Oct 2002, Samuel Flory wrote: > >>> > >>> > >>>>>On Wed, 16 Oct 2002, Mark Cuss wrote: > >>>>> > >>>>>This is the correct behavior. If you don't like this, you can > >>>>>swap motherboards with me ;) Otherwise, grin and bear it! > >>>>> > >>>>> > >>>> Wouldn't it be easier just to turn off the hypertreading or jackson > >>>>tech option in the bios ;-) > >>>> > >>>> > >>>Why would you ever want to turn it off? You paid for a CPU with > >>>two execution units and you want to disable one? This makes > >>>no sense unless you are using Windows/2000/Professional, which > >>>will trash your disks and all their files if you have two > >>>or more CPUs (true). > >>> > >>> > >>No, you're thinking of IBM's Power4 chip, which really does have two CPU > >> > >> > >cores > > > > > >>on one chip, sharing only the L2 cache. > >> > >>The P4 hyperthreading shares just about all CPU resources between the two > >>threads of execution. There are only separate registers, local APIC, and > >>some other minor logic for each "CPU" to call its own. All execution > >> > >> > >units > > > > > >>are demand shared between them. (The new "pause" opcode, rep nop, allows > >> > >> > >one > > > > > >>half to yield resources to the other half.) > >> > >>That's why typical job mixes only get around 20% improvement. Even > >> > >> > >optimized > > > > > >>benchmarks, which run only integer code on one side and floating point on > >> > >> > >the > > > > > >>other only get around a 40% boost. The P4 just doesn't have all that many > >>execution units to go around. Future chips will probably do better. > >> > >> > >> > >>>Cheers, > >>>Dick Johnson > >>>Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips). > >>>The US military has given us many words, FUBAR, SNAFU, now ENRON. > >>>Yes, top management were graduates of West Point and Annapolis. > >>> > >>> > >>-- > >>James Cleverdon > >>IBM xSeries Linux Solutions > >>{jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot com > >> > >>- > >>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > >>the body of a message to majordomo@vger.kernel.org > >>More majordomo info at http://vger.kernel.org/majordomo-info.html > >>Please read the FAQ at http://www.tux.org/lkml/ > >> > >> > >> > > > > > > > > > > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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