Re: [ath9k-devel] ath9k: massive unexplained latency in 2.6.27 (rc5, rc6, probably others)

Steven Noonan
2008-09-19T08:22:54Z

On Fri, Sep 19, 2008 at 1:17 AM, Ingo Molnar <mingo@elte.hu> wrote:
> in tip/master there's an ftrace_printk() facility. You can just replace
> the verbose printk()s with ftrace_printk() and see the result in
> /debug/tracing/trace.
>
> This sort of tracing has very low overhead and can be used in an easy
> ad-hoc manner with no extra infrastructure. Here's a few quick-start
> links about how to enable the scheduler tracer:
>
> http://redhat.com/~mingo/sched-devel.git/readme-tracer.txt
> http://redhat.com/~mingo/sched-devel.git/howto-trace-latencies.txt
>
> any ftrace_printk() you add in the kernel will show up in that trace.
>
> (If the scheduling events are uninteresting and clutter the output then
> you might want to remove the scheduler tracing entries from kernel/*.c
> by removing the trace_sched_*() calls or use a less noisy tracer.)
>
> to get enough of a trace history you might want to increase the number
> of trace entries in /debug/tracing/trace_entries from 16K to 128K or so.
>

Thanks for the suggestion, I'll do that. :)