htt & smp

[Alexandre "Sunny" Kovalenko]

On Tue, 2004-11-09 at 01:21, Randy Bush wrote:
> i have heard conflicting things, so thought i would ask.
> 
> for a server running a bunch of net aps, if the cpu is htt,
> is it worth turning on smp?
> 
> randy
> 
> ---
> 
> CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (2795.24-MHz 686-class CPU)
>   Origin = "GenuineIntel"  Id = 0xf34  Stepping = 4
>   Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>   Hyperthreading: 2 logical CPUs
> 
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On heavily computational multithreaded application (plenty of RC4 and
MD5 calculations done in parallel) two-way 2.8GHz Xeon without HTT was
~30% slower then same machine with HTT on (virtual 4-way), but machine
was running SMP kernel in both cases, and the application was somewhat
extreme. Then again, if you are terminating a lot of SSL sessions as
part of the "bunch of net aps", your case might not be that different.
On the other hand, this application scales almost linearly with addition
of the CPU (tested on real 4-way hardware), so 30% is not that much of a
gain.

I have no experience comparing UP vs. SMP, though...

HTH,
Alexandre "Sunny" Kovalenko.