Messages in this thread | | | Date | Thu, 31 Mar 2005 13:30:24 +0200 | From | Ingo Molnar <> | Subject | Re: 2.6.11, USB: High latency? |
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* kus Kusche Klaus <kus@keba.com> wrote:
> I'm performing realtime latency tests (for details about the hardware > and software, see my mail "[BUG] 2.6.11: Random SCSI/USB errors when > reading from USB memory stick" erlier today). > > Even when the errors described in my previous mail does not occur, > massive USB stick transfers cause latencies of 1 to 2 milliseconds, > which is way too much for realtime control systems.
do these occur under PREEMPT_RT? If yes, do you get any useful trace if you enable all the tracing options but keep wakeup-timing off:
# CONFIG_WAKEUP_TIMING is not set CONFIG_PREEMPT_TRACE=y CONFIG_CRITICAL_PREEMPT_TIMING=y CONFIG_CRITICAL_IRQSOFF_TIMING=y CONFIG_CRITICAL_TIMING=y CONFIG_LATENCY_TIMING=y CONFIG_LATENCY_TRACE=y CONFIG_MCOUNT=y
this should catch any type of preempt-off section, irqs-off and preempt_disable() alike. (unless the tracer has a bug.)
(WAKEUP_TIMING is useful and lightweight but if all other tracing features are enabled it's a bit pointless, and a bit less accurate.)
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