Re: Latency traces I cannot interpret (sa1100, 2.6.15-rc7-rt1)

[Daniel Walker <dwalker@mvista.com>]

Do you have any power management features turned on?

I've seen some traces that look like this on buggy intel x86 hardware.
When a small two line function with no loops lasts for 10ms . One of
your traces showed irq_exit() lasting 9ms . It's like the process just
stops.

Daniel

On Thu, 2005-12-29 at 16:08 +0100, kus Kusche Klaus wrote:
> I took some latency traces on our sa1100 (see attachment) running
> 2.6.15-rc7-rt1 with full preemption.
> They look very bad at the first glance, but I cannot interpret them in
> detail.
> 
> Trace 3, 4 and 5 seem to have obvious reasons: FPU emulation,
> Framebuffer console updates, and compression/decompression of flash data
> for jffs2.
> 
> Moreover, if I read these traces correctly, they just disable
> preemption, but still allow interrupts. Is that correct? Can anything be
> done against these latencies, i.e. do they really need to disable
> preemption for such a long time?
> 
> However, traces 1, 2, 6 and 7 are completely mysterious to me.
> Interrupts seem to be blocked for milliseconds, while nothing is going
> on on the system? Moreover, there are console-related function names in
> traces 6 and 7, although I've unconfigured the framebuffer console for
> these runs!
> 
> Many thanks in advance for any help!
> 
> Klaus Kusche
> Entwicklung Software - Steuerung
> Software Development - Control
> 
> KEBA AG
> A-4041 Linz
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