Hello Ingo,
I am using your yum-distributed kernel 2.6.19.1-rt15, and
unfortunately I experienced very worse latencies.
It turned out that ALL the IRQ threads were all running at prio 0, SCHED_OTHER.
Looking at the current code in kernel/irq/manage.c, the goal was to
put them at MAX_RT_PRIO, but the call to sys_sched_setscheduler()
fails with EINVAL. I have attached a patch to set them to
(MAX_RT_PRIO-1). This works.
Further I believe that each application of the RT-kernel requires a
different configuration of these thread-priorities and I prefer to
reconfigure these prios from userland during boot. As these
threadnames contain whitespaces in its name, they make the
shell-scripts unnecessary complex that I use to reconfigure the thread
priorities.
So, I would prefer a slight modification of the names: The attached
patch also changes the names from [IRQ nn] to [IRQ-nn]. I hope that
you agree with me here. (If not, I stick to do this patch each time
myself ;-) )
Kind Regards,
Remy B?hmer
* Remy Bohmer <[email protected]> wrote:
> Hello Ingo,
>
> I am using your yum-distributed kernel 2.6.19.1-rt15, and
> unfortunately I experienced very worse latencies. It turned out that
> ALL the IRQ threads were all running at prio 0, SCHED_OTHER.
>
> Looking at the current code in kernel/irq/manage.c, the goal was to
> put them at MAX_RT_PRIO, but the call to sys_sched_setscheduler()
> fails with EINVAL. I have attached a patch to set them to
> (MAX_RT_PRIO-1). This works.
oops - my intention was to set all IRQs and softirqs to SCHED_FIFO prio
50. I have fixed that now in my tree.
prio 99 is pretty extensive and makes it hard to move tasks 'above'
hardirq priority, without setting the priority of /every/ IRQ thread. So
i picked SCHED_FIFO:50 - at exact half way.
> Further I believe that each application of the RT-kernel requires a
> different configuration of these thread-priorities and I prefer to
> reconfigure these prios from userland during boot. As these
> threadnames contain whitespaces in its name, they make the
> shell-scripts unnecessary complex that I use to reconfigure the thread
> priorities.
ok - lets try it. Clark: does this impact the set_kthread_prio utility?
I've changed "IRQ 123" to "IRQ-123" to make pidof & friends work better.
Ingo
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Ingo Molnar wrote:
>
> ok - lets try it. Clark: does this impact the set_kthread_prio utility?
> I've changed "IRQ 123" to "IRQ-123" to make pidof & friends work better.
Yes it does, but I believe I can fix that. Most of the logic is in awk
and I believe one call to sub() will handle the change.
Clark
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