Re: Tweak Latency on Intel ATOM

["Max Müller" <mxmr@gmx.net>]

Clark Williams schrieb:
> On Mon, 15 Feb 2010 10:32:54 +0100
> Max Müller <mxmr@gmx.net> wrote:
>  
>   
>>> I'd say you're doing pretty good keeping under 50us. You might want to
>>> try it under a heavier load than the shell script you've been running.
>>> If you don't want to fool with rteval, try kicking off a kernel compile
>>> in another window like this:
>>>
>>> $ while true; do make -j4 clean bzImage modules; done
>>>
>>> and then run cyclictest. A kernel compile with parallel jobs (-j) is a
>>> good overall load of computation and I/O.
>>>
>>>   
>>>       
>> I tested now like you told me with irqbalance and cpuspeed services 
>> disabled. I hope i made the right for disabling irqbalance, i used the 
>> kernel parameter acpi_no_irqbalance. Is this correct? Unfortunately the 
>> results were nearly equal as before.
>>     
>
> I don't think you're going to get much better results on the Atom. I
> have an MSI Nettop box with the dual-core version and I saw about the
> same results as you.
>
> What sort of scheduling deadlines are you trying to meet? 
>
> Clark
>   
Shorter it is better it would be :-)
I can also live with this results, but i wanted to make sure to get the 
best out of this hardware.

Are you running both cores on the MSI box (maybe also with 
hyperthreading enabled) with this results?

In the meantime i thought also if the SMI (system management mode) could 
have a bad influence. I wrote a little userspace  programm which 
disables global SMI bit of the ICH7 southbridge. But also no better 
results.
After that i was told (thanks to Luis Claudio!) to check latency with 
the kernel module hwlat_detector. The results of this module was 0. I 
interpreted this that there is no SMI that causes the latency on my ATOM 
system.

Regards,
Max


--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html