RE: 2.6.11, IDE: Strange scheduling behaviour: high-pri RT process not scheduled?

["kus Kusche Klaus" <kus@keba.com>]

> > The following tests are made with 'IRQ 8' at 95, rtc_wakeup 
> at 89(99):
> > * Heavy mmap load, no oom: max jitter:     42.1% (   51 usec)
> > * Heavy mmap load, oom:    max jitter:  11989.2% (14635 usec)
> >   (but still "missed irqs: 0", so IRQ 8 was also blocked for 14 ms)
> 
> did you get any kernel messages in that time? (about missed 
> irqs, etc.)  
> Please do a 'dmesg -n 0' to minimize the effect of kernel messages.

Excellent, thanks!

It turned out that the latencies are not caused by the kernel
messages themselves, but by sending them to a serial console
(which was off), in all my high latency cases at rtpri 89(99).

After removing the serial console from the boot parameters,
* the OOM timings are back to normal (around 50 microseconds)
* the USB error and remove timings are back to normal
* the USB plugin timings are in the range of the USB read
  (which is up to 1 ms - still bad)

However, latencies at rtprio 2 are still very frustrating
(details will follow).

-- 
Klaus Kusche
Entwicklung Software - Steuerung
Software Development - Control

KEBA AG
A-4041 Linz
Gewerbepark Urfahr
Tel +43 / 732 / 7090-3120
Fax +43 / 732 / 7090-8919
E-Mail: kus@keba.com
www.keba.com
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