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SubjectRe: 2.6.14-rc3-rt2
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On Oct 5, 2005, at 9:08 AM, Thomas Gleixner wrote:

> On Wed, 2005-10-05 at 08:58 -0700, david singleton wrote:
>>>
>>> Yes. Thats happening. I moved the priority of softirq-timer above
>>> hackbench priority and the problem goes away. I look into this
>>> further.
>>
>> I had to set the threaded softirqs to real time priorities with the hi
>> thread at 24,
>> the timer thread at 23, net_rx at 22, etc. I wanted their
>> priorities
>> just below the IRQ threads.
>>
>> The problem was the timer thread. Other real time threads got in
>> its
>> way and held off timers.
>>
>> And I had to make a note if any higher priority apps depended on
>> timers
>> that the timer
>> thread had to be boosted in priority to match that real time threads
>> priority. It's like
>> the softirqd's timer thread needs priority inheritance.
>
> Well, we had implemented this in one of the previous -rt versions for
> the high resolution timers. It was a bit hacky and I did not come
> around
> to reimplement it on top of ktimers. This is only a problem for itimers
> and posix interval timers at the moment. The nanosleep variants do not
> suffer from this problem as the wakeup happens directly from the hr
> timer interrupt. That way we have only one instead of two task
> switches.

When I finally got the IRQ threads priorities straight and the softirqd
priorities
matched to be right underneath the IRQ priorities the system would run
any benchmark I could throw at it with no problems, modulo the strange
app that wanted to run at priority 99 and depended on itimers or
sigarlm . . .

For that case I had to match the softirq timer thread to that of the
app before
it would run with no problems.

David
>
> tglx
>
>
>
>

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