Messages in this thread | | | Date | Wed, 16 Oct 2002 13:47:32 -0700 | From | Samuel Flory <> | Subject | Re: Kernel reports 4 CPUS instead of 2... |
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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/ >> >> >> > > > >
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