[Xenomai-core] Regarding enabling SMP with Xenomai

[Xenomai-core] Regarding enabling SMP with Xenomai

[Shashank Bhatia]

Dear All,
              I have been trying to install Xenomai on my Dual Core
Intel Machine. This CPU has 2 cores, so i wanted to enable the SMP flag
in the kernel configuration.

I started with downloading kernel ver 2.6.25.11 from kernel.org, and got
adeos patch as well as xenomai-2.4.7 downloaded. I used the
prepare-kernel script for patching. 

When i go to the make menuconfig. The real time subsystem section gives
a meassage that either the HPET_TIMER must be turned off or
X68_LOCAL_APIC must be turned off. 

After a lot of trials, i failed to find the options for turning of the
X86_LOCAL_APIC flag. 

Then i went on to fiddle and do some trials. 

I tried with subarchitecture type PC compatible, and the Processor type
to be Core2 or newer. The xenomai gets installed, but the latency i get
is really high. I am getting a maximum latency of around 30 us and even
this is not constant. it varies a lot. 

After some googling i found that i must have the SMI workaround. 
I enabled that and recompiled my kernel. But could not get good
latencies still.

Now please guide me as to how can i have the SMP enabled. I want that
the OS must use both the Cores of my CPU. 

Please also suggest if there is some documentation i can read to achieve
lower latencies.


Thanks in Advance

Shashank



-------------------------------------
Hi-Tech Gears Limited, Gurgaon, India

Re: [Xenomai-core] Regarding enabling SMP with Xenomai

[Gilles Chanteperdrix]

Shashank Bhatia wrote:
> Dear All,
>               I have been trying to install Xenomai on my Dual Core
> Intel Machine. This CPU has 2 cores, so i wanted to enable the SMP flag
> in the kernel configuration.
> 
> I started with downloading kernel ver 2.6.25.11 from kernel.org, and got
> adeos patch as well as xenomai-2.4.7 downloaded. I used the
> prepare-kernel script for patching. 

These are outdated versions. Especially on x86, especially with SMP
configuration. So, please use the latest stable release of Xenomai
(xenomai-2.4.8), using the I-pipe patches it proposes. And we also would
be interested if you could test of the release candidate which has just
been released.

> 
> When i go to the make menuconfig. The real time subsystem section gives
> a meassage that either the HPET_TIMER must be turned off or
> X68_LOCAL_APIC must be turned off. 
> 
> After a lot of trials, i failed to find the options for turning of the
> X86_LOCAL_APIC flag. 

That is because SMP mode needs local APIC, so, if you want to disable
local APIC, you need to disable SMP. But I think you misunderstood the
message, the message is: "NOTE: Xenomai needs either X86_LOCAL_APIC
enabled or HPET_TIMER disabled.", so what you should do is disable
HPET_TIMER.

> 
> Then i went on to fiddle and do some trials. 
> 
> I tried with subarchitecture type PC compatible, and the Processor type
> to be Core2 or newer. The xenomai gets installed, but the latency i get

You should always choose the processor which you really have, this is in
the FAQ too.

> is really high. I am getting a maximum latency of around 30 us and even
> this is not constant. it varies a lot. 

30us is a bit high, but not that high. An SMI induced latency is
something larger than, say, 80us. You should try more recent releases to
see if you get better results.

> 
> After some googling i found that i must have the SMI workaround. 
> I enabled that and recompiled my kernel. But could not get good
> latencies still.

Why using Google? Xenomai documentation is available on Xenomai site.
The SMI option is described in an FAQ. And also in the TROUBLESHOOTING
option which comes with Xenomai sources.

-- 
					    Gilles.

Re: [Xenomai-core] Regarding enabling SMP with Xenomai

[Shashank Bhatia]

Thanks a lot Gilles,

I used the Xenomai 2.4.8 version with a newer kernel 2.6.28.9 to be
precise.

Initially the kernel compilation gave error of NR_CPU flag, i lowered
the no of CPUs to 16 and it worked.

Now the xenomai is able to see two CPUs, the output
of /proc/xenomai/sched is :
CPU  PID    PRI      PERIOD     TIMEOUT    TIMEBASE  STAT       NAME
  0  0       -1      0          0          master    R          ROOT/0
  1  0       -1      0          0          master    R          ROOT/1



The output of dmesg |grep is
[    4.353912] I-pipe: Domain Xenomai registered.
[    4.353949] Xenomai: hal/i386 started.
[    4.354530] Xenomai: real-time nucleus v2.4.8 (Lords Of Karma)
loaded.
[    4.354612] Xenomai: SMI-enabled chipset found
[    4.354623] Xenomai: SMI workaround enabled
[    4.354647] Xenomai: starting native API services.
[    4.354650] Xenomai: starting POSIX services.
[    4.354693] Xenomai: starting RTDM services.



Thanks for your help..

Now i am facing just a small issue, i think the pipes for klatency tests
are not created, thats why when i run the klatency test, i get the error
as:
root@domain.hid# ./run 
*
*
* Type ^C to stop this application.
*
*
open(/proc/xenomai/registry/native/pipes/klat_pipe): No such file or
directory
modprobe klat_mod or try the -P option?


Please tell me if i am doing something wrong.


Thanks again!


Regards,
Shashank





On Sat, 2009-06-20 at 15:42 +0200, Gilles Chanteperdrix wrote:
> Gilles


-------------------------------------
Hi-Tech Gears Limited, Gurgaon, India

Re: [Xenomai-core] Regarding enabling SMP with Xenomai

[Gilles Chanteperdrix]

[-- Attachment #1: Type: text/plain, Size: 778 bytes --]

Shashank Bhatia wrote:
> Thanks a lot Gilles,
> 
> I used the Xenomai 2.4.8 version with a newer kernel 2.6.28.9 to be
> precise.

You are still posting to the wrong list. I will not answer, since
otherwise you will continue ignoring me when I tell you that you are
posting to the wrong list.

The mail address with which you registered to the Xenomai mailing list
causes bounces. So, please use another address (gmail, yahoo, even
hotmail, whatever you want, but not a server which bounces the xenomai
mails). See the attached bounce.

Also note that posting a mail to a public mailing list with a disclaimer
saying that the mail is not public is stupid, since you are posting to a
public mailing list in the first place.

-- 
                                          Gilles


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Hi-Tech Gears Limited, Gurgaon, India