Re: [Xenomai-help] Very high latencies under stress testing

[edward.robbins@domain.hid]

On Friday, 13 August, 2010 3:35pm, "Gilles Chanteperdrix" <gilles.chanteperdrix@domain.hid> said:

> edward.robbins@domain.hidk wrote:
>>
>> I wonder if this is to do with graphics? I have set "NoAccel" in the
>> driver section of Xorg.conf (I am using fbdev). I also notice that
>> latencies go massive (e.g. 4200uS) the first time I run glxgears.
>> "glxinfo" reports "Direct rendering: no".
> 
> This is bad news. It could come either from the fact that the Xorg
> driver shuts hardware interrupts off (there is nothing xenomai can do
> about that), or it could be an SMI issue. What about using the driver
> for the real graphic card you have ? Probably intel card? Do you observe
> any big latencies if you stress the system with anything else than X?
> 
>> Power management options (ACPUI, APM): Disable ACPI (Advanced
>> Configuration and Power Interface) Support --> Processor Disable CPU
>> Frequency Scaling Disable CPU idle PM support Disable Power Managment
>> Support
> 
> Disabling ACPI is a bad idea. As repeated many times, only
> ACPI_PROCESSOR should be disabled, not ACPI.
> 

Thanks for your helpful responses.

I'm not working on this project again until next week, but on Friday I was able to

 o Recompile the kernel with ACPI enabled 
 o Boot with the 'SMI handler' BIOS option set to disabled....
   according to the help text this option should be disabled if 'an RTOS 
   is installed' - I presume this means that SMIs are completely disabled 
   and therefore SMIs cannot be the source of the problem 
  (very convenient BIOS option... now I begin to appreciate the expense of this board!) 
 o Changed xorg to use the intel video driver

After doing this I still have problems with latencies and X, but did not have a chance to stress the system with non-graphics tasks. I am thinking that when I get back to it next week I will compile the kernel a few times and also try writing a large file a number of times to the disk as Philippe suggested. Hopefully this will not cause any problems and I can then more confidently attribute the high latency to the graphics system. I will also attempt to install the I-pipe tracer as suggested. I'll update when (if!?) I get that far.

Thanks
Edward