Re: [Xenomai] i-pipe tracer on in production kernels? (was Re: Altera Cyclone V)

[Philippe Gerum <rpm@xenomai.org>]

On 01/11/2014 11:22 AM, Michael Haberler wrote:
>
> http://www.xenomai.org/index.php/I-pipe:Tracer describes the trace API, which could be useful to track down issues
>
> Q: does enabling the tracer incur significant overhead if compiled in but unused, or is it reasonable to leave it on in a production kernel?
>
> if the former, we might have to build/make available a second i-pipe tracer enabled kernel to track down issues 'in the field'; if the latter, it'd be less build/distribution chores
>

The I-pipe tracer is based on the ftrace infrastructure, so tracepoints 
are left out when the tracer is disabled. If you can live with the 
minimal overhead ftrace adds, then leaving the I-pipe tracer code built 
in may be an option.

> thanks in advance,
>
> Michael
>
>
>
> Am 08.01.2014 um 01:51 schrieb Charles Steinkuehler <charles@steinkuehler.net>:
>
>> On 1/7/2014 5:13 PM, Gilles Chanteperdrix wrote:
>>> On 01/07/2014 11:55 PM, Charles Steinkuehler wrote:
>>>> On 1/7/2014 4:47 PM, Gilles Chanteperdrix wrote:
>>>>> On 01/07/2014 11:19 PM, Charles Steinkuehler wrote:
>>>>>> The single-core A8 on the BeagleBone is good for about 25 uS
>>>>>> typical and 80 uS or so worst case latency.
>>>>>
>>>>> That is really high. On a 720MHz OMAP3, with the latency test
>>>>> running with a 100us period, I typically get latencies close to
>>>>> 40us (under dohell load). Granted I do not run many
>>>>> functionalities of the SOC (typically, not the graphic
>>>>> processor), but I would not expect latencies to get so high. Is
>>>>> there any chance you could trigger a trace with the I-pipe
>>>>> tracer?
>>>
>>>> I can try...give me a while to sort through the I-pipe:Tracer wiki
>>>> page (or are there better instructions?).
>>>
>>> Enable I-pipe tracer in kernel configuration, especially
>>> IPIPE_TRACE_MCOUNT, and IPIPE_TRACE_VMALLOC.
>>>
>>> When the system has booted, do:
>>
>> <snip>
>>
>> Thanks for the details!  My to-do list just got longer...  :)
>>
>> I'll do some testing (on the BeagleBone) and post the results, but it
>> might take a couple of days.
>>
>> FYI, the GPU is currently disabled on the BeagleBone, so no mysterious
>> latency from that source (hopefully).  I need to migrate to a 3.12
>> kernel to get the GPU working (and it doesn't currently support X11,
>> only framebuffer applications), which is part of why I'm interested in
>> Xenomai on the 3.10 or newer kernel for the Cyclone-V SoC.
>>
>> --
>> Charles Steinkuehler
>> charles@steinkuehler.net
>>
>> -------------- next part --------------
>> A non-text attachment was scrubbed...
>> Name: signature.asc
>> Type: application/pgp-signature
>> Size: 261 bytes
>> Desc: OpenPGP digital signature
>> URL: <http://www.xenomai.org/pipermail/xenomai/attachments/20140107/99bb4e74/attachment.sig>
>> _______________________________________________
>> Xenomai mailing list
>> Xenomai@xenomai.org
>> http://www.xenomai.org/mailman/listinfo/xenomai
>
>
> _______________________________________________
> Xenomai mailing list
> Xenomai@xenomai.org
> http://www.xenomai.org/mailman/listinfo/xenomai
>


-- 
Philippe.