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SubjectRe: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.30-2
Ingo Molnar wrote:
> * Eran Mann <> wrote:
>>I´m seeing latencies of up to ~2000 microseconds. see attached traces
>>file for a small sample. I think I´m missing something obvious
>>config-wise but I don´t know what...

> this seems to imply IDE DMA related hardware overhead. Apparently what
> happens is that with certain motherboards/chipsets, if IDE DMA happens
> then that DMA transfer _completely locks up_ the system bus. Nothing
> happens, and the CPU is stalled in essence until the end of the DMA
> request.
> Ingo

Right on.
After hdparm -d0 I see maximum latency of 35 us after a full kernel
build with a few GUI apps in the background. I´ll try to find a
reasonable compromise.
Eran Mann
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