Messages in this thread | | | Date | Fri, 19 Sep 2008 01:45:11 -0700 | From | "Steven Noonan" <> | Subject | Re: [ath9k-devel] ath9k: massive unexplained latency in 2.6.27 (rc5, rc6, probably others) |
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On Fri, Sep 19, 2008 at 1:22 AM, Steven Noonan <steven@uplinklabs.net> wrote: > 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. :) >
It'd be extremely convenient to have a tracer that did absolutely nothing but display ftrace_printk()s.
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