From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 12 Oct 2007 16:21:51 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-help] awful latencies (~110us)
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To: CHABAL David <david.chabal@domain.hid>
Cc: xenomai@xenomai.org

CHABAL David wrote:
> Philippe Gerum a =E9crit :
>>
>> I suspect the tracer to induce massive cache misses on your setup, whi=
ch
>> limits the interpretation we can have of this log. Could you apply the
>> following patch, and post back the frozen log for the very same test?
>> TIA,
>>
>> --- 2.6.20-ipipe-1.8-08/kernel/ipipe/core.c~    2007-09-16
>> 16:54:34.000000000 +0200
>> +++ 2.6.20-ipipe-1.8-08/kernel/ipipe/core.c    2007-10-10
>> 13:05:28.000000000 +0200
>> @@ -283,7 +283,7 @@
>>      unsigned long flags;
>>      int s;
>> =20
>> -    local_irq_save_hw(flags);
>> +    local_irq_save_hw_notrace(flags);
>>      __raw_spin_lock(lock);
>>      ipipe_load_cpuid();
>>      ipd =3D per_cpu(ipipe_percpu_domain, cpuid);
>> @@ -302,7 +302,7 @@
>>      ipd =3D per_cpu(ipipe_percpu_domain, cpuid);
>>      if (!raw_demangle_irq_bits(&x))
>>          __clear_bit(IPIPE_STALL_FLAG, &ipd->cpudata[cpuid].status);
>> -    local_irq_restore_hw(x);
>> +    local_irq_restore_hw_notrace(x);
>>  }
>> =20
>>  /*
>>
> The freeze file enclosed is generated with this patch and the i8259.c
> patch.
>=20
> ---|------------|------------|------------|--------|-------------------=
------
>=20
> RTS|       5.570|       9.400|      85.356|       0|    00:08:55/00:08:=
55
>=20
> Should I try without the I-pipe debugger ?

Never say never, but the tracer most probably not causing these
latencies. Currently, all points to the good-old programmable interrupt
controller.

Do you have CONFIG_X86_UP_IOAPIC enabled? If no, please try to do so.

Jan

--=20
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux