On 02/29/2012 08:59 PM, Charles Lesire-Cabaniols wrote:
> 2012/2/29 Gilles Chanteperdrix <[email protected]>
>
>> On 02/29/2012 08:44 PM, Charles Lesire-Cabaniols wrote:
>>> 2012/2/29 Gilles Chanteperdrix <[email protected]>
>>>
>>>> On 02/29/2012 07:03 PM, Charles Lesire-Cabaniols wrote:
>>>>> 2012/2/29 Gilles Chanteperdrix <[email protected]>
>>>>>
>>>>>> On 02/29/2012 06:52 PM, Charles Lesire-Cabaniols wrote:
>>>>>>> 2012/2/29 Gilles Chanteperdrix <[email protected]>
>>>>>>>
>>>>>>>> On 02/29/2012 06:29 PM, Charles Lesire-Cabaniols wrote:
>>>>>>>>> Hi guys,
>>>>>>>>>
>>>>>>>>> I have installed a Debian+Xenomai (2.6.0) OS on my Gumstix Overo.
>>>>>>>>>
>>>>>>>>> I want to evaluate the execution time of a simple program, executed
>>>> as
>>>>>> a
>>>>>>>>> real-time thread.
>>>>>>>>>
>>>>>>>>> I definitely wonder about which functions to use, as I have
>>>> completely
>>>>>>>>> inconsistent measures.
>>>>>>>>> I have tried using rt_timer_read, rt_timer_tsc, clock_gettime.
>>>>>>>>> I also directly read the CNNT register with ARM instructions (which
>>>> is
>>>>>>>> the
>>>>>>>>> only one I think correct) in order to have a (good?) reference.
>>>>>>>>> (...)
>>>>>>>>> What am I doing wrong?
>>>>>>>>
>>>>>>>> So, you should printf("%Lu %Lu\n", rt_timer_read(), rt_timer_tsc());
>>>>>>>>
>>>>>>>> Not printf("%lu", ...)
>>>>>>>>
>>>>>>>> --
>>>>>>>> Gilles.
>>>>>>>>
>>>>>>>
>>>>>>> Effectively, that looks cleaner, thanks:
>>>>>>>
>>>>>>> ----- Xenomai rt_timer_read -----
>>>>>>> start: 49166276042 ; end: 49166432273 ; (s-e): 156231 ; CET: 156231
>>>>>>> ----- Xenomai rt_timer_tsc -----
>>>>>>> start: 639161547 ; end: 639163539 ; (s-e): 1992 ; CET: 1992
>>>>>>> ----- Xenomai clock_gettime -----
>>>>>>> [ s] start: 946684855 ; end: 946684855 ; (s-e): 0 ; CET: 0
>>>>>>> [ns] start: 275520245 ; end: 275677089 ; (s-e): 156844 ; CET: 156844
>>>>>>>
>>>>>>> My ARM instruction reads 110554.
>>>>>>>
>>>>>>> Which Xenomai function should I use?
>>>>>>> Which one is supposed to be the more accurate?
>>>>>>> Does rt_timer_read return nsecs?
>>>>>>> What is the unit of rt_timer_tsc?
>>>>>>
>>>>>> rt_timer_tsc uses whatever hardware counter is available, you need
>>>>>> rt_timer_tsc2ns or rt_timer_ns2tsc to convert between this unit to and
>>>>>> from nanoseconds.
>>>>>>
>>>>>> For more details, see:
>>>>>>
>>>>>>
>>>>>>
>>>>
>> http://www.xenomai.org/documentation/xenomai-2.6/html/api/group__native__timer.html
>>>>>>
>>>>>> Depending on how xenomai user-space was compiled, rt_timer_tsc should
>>>>>> have the lowest overhead.
>>>>>>
>>>>>
>>>>> And are the default options the best ones?
>>>>
>>>> Yes, but I am not sure the debian package uses the default one. Please
>>>> post here the disassembly of rt_timer_tsc, I will tell you if your
>>>> system is compiled for the lowest overhead.
>>>>
>>>>
>>> How to do that?
>>
>> arm-none-linux-objdump -d /path/to/libnative.so.3 | less
>> search <rt_timer_tsc>, when you find it, post the disassembly here.
>>
>
> Here it is:
>
> 00005a54 <rt_timer_tsc>:
> 5a54: e59f2034 ldr r2, [pc, #52] ; 5a90
> <rt_timer_tsc+0x3c>
> 5a58: e3e03a0f mvn r3, #61440 ; 0xf000
> 5a5c: e59f1030 ldr r1, [pc, #48] ; 5a94
> <rt_timer_tsc+0x40>
> 5a60: e08f2002 add r2, pc, r2
> 5a64: e5133003 ldr r3, [r3, #-3]
> 5a68: e7921001 ldr r1, [r2, r1]
> 5a6c: e59f0024 ldr r0, [pc, #36] ; 5a98
> <rt_timer_tsc+0x44>
> 5a70: e2833003 add r3, r3, #3
> 5a74: e0403283 sub r3, r0, r3, lsl #5
> 5a78: e92d4010 push {r4, lr}
> 5a7c: e5910008 ldr r0, [r1, #8]
> 5a80: e1a0e00f mov lr, pc
> 5a84: e12fff13 bx r3
> 5a88: e8bd4010 pop {r4, lr}
> 5a8c: e12fff1e bx lr
> 5a90: 000086a4 andeq r8, r0, r4, lsr #13
> 5a94: 000000ec andeq r0, r0, ip, ror #1
> 5a98: ffff1004 undefined instruction 0xffff1004
This is the good one.
--
Gilles.
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