Re: 2.6.11, USB: High latency?

[Ingo Molnar]

* kus Kusche Klaus <kus@xxxxxxxx> 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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