Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758016AbYGKAC3 (ORCPT ); Thu, 10 Jul 2008 20:02:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754689AbYGKACV (ORCPT ); Thu, 10 Jul 2008 20:02:21 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:39638 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754074AbYGKACU (ORCPT ); Thu, 10 Jul 2008 20:02:20 -0400 Date: Thu, 10 Jul 2008 20:02:18 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Randy Dunlap cc: Elias Oltmanns , LKML , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Clark Williams , Linus Torvalds , Andrew Morton , Jon Masters Subject: Re: [PATCH] ftrace: Documentation In-Reply-To: <20080710132832.38cc5048.randy.dunlap@oracle.com> Message-ID: References: <87zlop7bp6.fsf@denkblock.local> <20080710132832.38cc5048.randy.dunlap@oracle.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5343 Lines: 208 On Thu, 10 Jul 2008, Randy Dunlap wrote: > [I'm dropping good comments, just making more comments.] This is why I CC'd you ;-) > > > > + set_ftrace_notrace: This has the opposite effect that > > > + set_ftrace_filter has. Any function that is added > > > + here will not be traced. If a function exists > > > + in both set_ftrace_filter and set_ftrace_notrace > > > > (comma) > > > > > + the function will _not_ bet traced. > > be Sorry, it has a gambling problem. > > > > + stacktrace - This is one of the options that changes the trace itself. > > > > change > > changes :) [subject is "This", singular] Woot! I'm actually right?? Nah, this can't be. Maybe my mom did speak good english. ;-) > > > > > > + When a trace is recorded, so is the stack of functions. > > > + This allows for back traces of trace sites. > > > + > > > +sched_switch > > > +------------ > > > + > > > +This tracer simply records schedule switches. Here's an example > > > +on how to implement it. > > of OK > > > > > use? > > > > [...] > > > +Here we traced a 50 microsecond latency. But we also see all the > > > +functions that were called during that time. Note that enabling > > > > by enabling? > > > > > +function tracing we endure an added overhead. This overhead may > > > > (comma) > > > > > +extend the latency times. But never the less, this trace has provided > > nevertheless, It is one word? I wrote that first and then thought that it was wrong. > > > > +some very helpful debugging. > > > > debugging information? Sure. > > > > > + > > > + > > > +preemptoff > > > +---------- > > > + > > > +When preemption is disabled we may be able to receive interrupts but > > > > (comma) > > > > > +the task can not be preempted and a higher priority task must wait > > cannot OK > > > > +for preemption to be enabled again before it can preempt a lower > > > +priority task. > > > + > > > +The preemptoff tracer traces the places that disables preemption. > > > > disable > > > > > +Like the irqsoff, it records the maximum latency that preemption > > > +was disabled. The control of preemptoff is much like the irqsoff. > > > > > +Since this tracer only deals with RT tasks, we will run this slightly > > > +different than we did with the previous tracers. Instead of performing > > differently OK > > > > +an 'ls' we will run 'sleep 1' under 'chrt' which changes the > > > > (comma) > > > > > +priority of the task. > > > [...] > > > +Where as the setting of the NEED_RESCHED bit happens on the > > Whereas OK > > > > +task's stack. But because we are in a hard interrupt, the test > > ^? That's not a complete sentence. I rewrote this part. So I'm not ignoring these comments. > > > > +is with the interrupts stack which has that to be false. We don't > > interrupt > > > > ^^^^ > > Superfluous that? Don't understand that sentence. > > > > > +see the 'N' until we switch back to the task's stack. > > [...] > > > +When dynamic ftrace is initialized, it calls kstop_machine to make it > > ^^ what is "it"? s/it/the machine/ > > > > +act like a uniprocessor so that it can freely modify code without > > > +worrying about other processors executing that same code. At > > > +initialization, the mcount calls are change to call a "record_ip" > > > > changed > > > > > +function. After this, the first time a kernel function is called, > > > +it has the calling address saved in a hash table. > > [...] > > > +Two files that contain to the enabling and disabling of recorded > > > +functions are: > > > > Can this be expressed somewhat differently? > > or drop "to". I rewrote this part too. > > > > > > + > > > + set_ftrace_filter > > > + > > > +and > > > + > > > + set_ftrace_notrace > > > + > > > +A list of available functions that you can add to this files is listed > > > > these > > > > > +in: > > > + > > > + available_filter_functions > > [...] > > > +Perhaps this isn't enough. The filters also allow simple wild cards. > > > +Only the following is currently available > > Only the following are currently available: OK > > > > + > > > + * - will match functions that begins with > > > > begin > > > > > + * - will match functions that end with > > > + ** - will match functions that have in it Thanks Randy, once again you helped me out in my documentation. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/