Messages in this thread | | | Date | Tue, 17 Dec 2002 14:27:04 -0500 (EST) | From | Bill Davidsen <> | Subject | Re: HT Benchmarks (was: /proc/cpuinfo and hyperthreading) |
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On Mon, 16 Dec 2002, J.A. Magallon wrote:
> Number of threads Elapsed time User Time System Time > 1 53:216 53:220 00:000 > 2 29:272 58:180 00:320 > 3 27:162 1:21:450 00:540 > 4 25:094 1:41:080 01:250 > > Elapsed is measured by the parent thread, that is not doing anything > but wait on a pthread_join. User and system times are the sum of > times for all the children threads, that do real work. > > The jump from 1->2 threads is fine, the one from 2->4 is ridiculous... > I have my cpus doubled but each one has half the pipelining for floating > point...see the user cpu time increased due to 'worst' processors and > cache pollution on each package. > > So, IMHO and for my apps, HyperThreading is just a bad joke.
I must be misreading this, it looks to me as though having threads running HT is reducing the clock time, and frankly that's what I want. It may not be as good as having more processors, but it certainly is better for nothing, even for your application. I read that as about 10% faster, and I know people who spend more on fans to o/c their CPU than the premium for a Xeon.
More to the point, since you have no choice if you want to go fast or have >2 CPUs, you get HT included. Clearly if you want good latency you don't run SMP at all due to the extra locking, that's a kernel issue, not HT.
-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
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