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 Böhmer
fix-kernel-irq-thread-prio.patch
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