Re: [Xenomai-help] bring down the system

[Jonas Buchli <jonas@domain.hid>]

wolfgang,

did you compile with exactly our compile statement or with additional 
flags (i.e. optimization)?

compiling with our statement, just throwing in the -S flag, i am getting 
a very getting different assembly code - while has been a while i have 
been reading assembly, it seems our loop is not getting optimized away.

anyway, the point here is not about if this is a meaningful program or 
not, but we are getting system lock ups and this one is a minimal 
program that does reproduce the problem for us.

best
jonas

Wolfgang Denk wrote:
> Dear Stefan Schaal,
> 
> In message <C790DE41-A093-46C5-9F44-D3F0EA839CF5@domain.hid> you wrote:
>> Sorry, I attached the wrong C-program in the previous posting ....  
>> here is the corrected version:
> 
> I'm not sure what exactly you are trying to test, but I think you
> should invest a little more time in your test cases.
> 
>>   attached is a little C program that spawns off a task which runs a  
>> heavy tiny math job. Despite my 8 processor machine, taking this one  
> 
> Does it? Not for me.
> 
>> void
>> run_task(void *dummy)
>> {
>>    int i;
>>    double foo = 1.0;
>>
>>    for (i=1; i<=100000000; ++i)
>>      foo = foo*1.1;
>>
>>    return;
>> }
> 
> On x86, this code compiles for me into this:
> 
>         .text
>         .p2align 4,,15
> .globl run_task
>         .type   run_task, @function
> run_task:
>         pushl   %ebp
>         movl    %esp, %ebp
>         popl    %ebp
>         ret
>         .size   run_task, .-run_task
>         .ident  "GCC: (GNU) 4.4.1 20090725 (Red Hat 4.4.1-2)"
>         .section        .note.GNU-stack,"",@progbits
> 
> Similar on ARM and Power.
> 
> As you can see, the compiler completely optimizes away your "tiny math
> job". So what should be loading your CPU?
> 
> Best regards,
> 
> Wolfgang Denk
> 

-- 
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Jonas Buchli, Dr.sc., MSc EE
Computational Learning and Motor Control Lab
University of Southern California
http://www-clmc.usc.edu/
+1 (213) 740 67 17
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