Load at 1.00 on SMP machine

Axel S. Gruner liste at encephalon.de
Mon Nov 21 17:21:03 GMT 2005


Am 21.11.2005 um 16:17 schrieb <myfreebsd at cox.net> <myfreebsd at cox.net>:

>> i got a Problem on my dual XEON 3.06 GhZ machine, 2GB of >RAM,  
>> FreeBSD
>> 5.4-STABLE.
>> I got "option SMP" in the kernel config and  
>> >"machdep.hlt_logical_cpus=1" in
>> /boot/loader.conf.
>> There are just 20 processes running (typical ones like >getty and  
>> stuff) and
>> the load of this machine is at 1.xx. There is no bgfsck and >other  
>> stuff.
>> So, i built a new kernel without "option SMP", rebooted, >and the  
>> load was
>> at 0.0x. But only one CPU was used (detected).
>> So, what could bei the Problem?
>> Well, the machine shows me 4 CPUs, HTT is not enabled via >/boot/ 
>> loader.conf
>> and "machdep.hyperthreading_allowed". So, how to disable >HTT?  
>> Maybe this is
>> the problem of the high load?
> Why are you setting machdep.hlt_logical_cpus=1? My understanding,  
> this would turn off one of the cpus. It should be set to 0 to have  
> both cpus going. Also it is set in sysctl.conf not loader.conf, at  
> least, that is how I have it.

Both CPUs are working. Also, works with machdep in loader.conf.
Thats not the problem.

> I am also curious how machdep.hyperthreading_allowed works. I run 6  
> so I believe it is turned on by default. Is this correct? Also if  
> it is a solo cpu with HTT, do you need option SMP and  
> machdep.hlt_logical_cpus=0 set or not with  
> machdep.hyperthreading_allowed on?

I do not know. I just want turn off HTT, but stay with SMP. So i want  
my two phyiscal CPUs working, but not the logical (HTT) one.
This is because is think maybe the load of 1.0x comes from turning on  
HTT. Well, if i do not use SMP in the kernel, the load is fine, but  
there is just one of the physical CPUs working.

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