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SubjectRe: 2.6.11, USB: High latency?

* kus Kusche Klaus <kus@keba.com> wrote:

> IRQ 7-724 0d..1 1us : end_8259A_irq (do_hardirq)
> IRQ 7-724 0d..1 1us!: enable_8259A_irq (do_hardirq)
> IRQ 7-724 0d... 832us : do_hardirq (do_irqd)
> IRQ 7-724 0d... 833us : trace_irqs_on (do_hardirq)

> mmap-1000 0d.h1 21us : end_8259A_irq (__do_IRQ)
> mmap-1000 0d.h1 22us!: enable_8259A_irq (__do_IRQ)
> mmap-1000 0d.h. 662us : irq_exit (do_IRQ)
> mmap-1000 0d..1 662us : do_softirq (irq_exit)

> mmap-1000 0d.h. 0us : do_IRQ (c012d6d5 7 0)
> mmap-1000 0d.h1 2us!: mask_and_ack_8259A (__do_IRQ)
> mmap-1000 0d.h1 938us : redirect_hardirq (__do_IRQ)
> mmap-1000 0d.h1 939us : wake_up_process (redirect_hardirq)

such 'freezes' almost certainly signal some sort of hardware latency -
some device holding the system bus up during DMA. There is no
algorithmic reason for any of those steps above to take several hundreds
of microseconds.

Ingo
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