Return-path: Received: from nf-out-0910.google.com ([64.233.182.185]:47151 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751023AbYISIWn (ORCPT ); Fri, 19 Sep 2008 04:22:43 -0400 Received: by nf-out-0910.google.com with SMTP id d3so117225nfc.21 for ; Fri, 19 Sep 2008 01:22:41 -0700 (PDT) Message-ID: (sfid-20080919_102247_518281_CCEDD395) Date: Fri, 19 Sep 2008 01:22:41 -0700 From: "Steven Noonan" To: "Ingo Molnar" Subject: Re: [ath9k-devel] ath9k: massive unexplained latency in 2.6.27 (rc5, rc6, probably others) Cc: "Luis R. Rodriguez" , "Luis Rodriguez" , "ath9k-devel@lists.ath9k.org" , linux-wireless , LKML In-Reply-To: <20080919081733.GC19491@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <20080918220102.GE7408@tesla> <43e72e890809181508w5232a14ewbf2bf18fe90a92d5@mail.gmail.com> <43e72e890809181610h3a7729d8s4c8484d97b21932e@mail.gmail.com> <20080919030125.GG7408@tesla> <20080919081733.GC19491@elte.hu> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Fri, Sep 19, 2008 at 1:17 AM, Ingo Molnar 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. :)