bizarre performance issues in 6.2 release

Cheffo cheffo at
Sat Feb 17 10:25:25 UTC 2007

Hi all,

garcol at wrote:
> See  kern/83406: [smp] em/bge drivers: severe performance loss under SMP
> sysctl machdep.cpu_idle_hlt=0
> (sysctl machdep.hyperthreading_allowed=1)

What actually do this ? (sysctl machdep.cpu_idle_hlt=0)

 From this PR (kern/83406) it seems that if you want full performance
you need machdep.cpu_idle_hlt=0 and machdep.hyperthreading_allowed=0
or machdep.cpu_idle_hlt=1 and machdep.hyperthreading_allowed=1, and 
others combination drop performance ..

Am I getting it right ?
And if yes why by default HT is disable, but machdep.cpu_idle_hlt is 
enabled ?

I'm little confused :)

> Regards
> Alessandro
>> Try disabling hyperthreading on the 6.2-server. In some cases you get
>> a moderate performance-increase, in most cases this setting is
>> counter-productive.
>> regards
>> Claus
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Best Wishes,
Stefan Lambrev
ICQ# 24134177

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