Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933702AbZAPXAY (ORCPT ); Fri, 16 Jan 2009 18:00:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757700AbZAPXAK (ORCPT ); Fri, 16 Jan 2009 18:00:10 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:57125 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757385AbZAPXAJ (ORCPT ); Fri, 16 Jan 2009 18:00:09 -0500 Date: Fri, 16 Jan 2009 23:59:48 +0100 From: Ingo Molnar To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Andrew Morton , Frederic Weisbecker , Chris Mason Subject: Re: [PATCH 0/2] ftrace: updates to tip Message-ID: <20090116225948.GA12314@elte.hu> References: <20090116004050.273665842@goodmis.org> <20090116112345.GC20082@elte.hu> <20090116152103.GA28643@elte.hu> <20090116160202.GA15209@elte.hu> <20090116163021.GA27495@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090116163021.GA27495@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2517 Lines: 66 * Ingo Molnar wrote: > > I was afraid you would say that :-) > > > > Yes, we could add something to do this. It would take some thought on > > a good api, and implementation. This is not an easy task by any means. > > We need a way to map between a function call and a tracer, where a > > function call can call more than one tracer. > > Note that some other things could be consolidated under per function > metadata: for example set_graph_function - which really is a per > function attribute too. Plus a lot of new things would be enabled i > think. a few other things that could be per-function attributes: - Using function trace 'limits': trace a function 50 times and dont trace it afterwards. Each invocation of that function decreases the remaining-count by one. For example: echo 'btrfs_join_transaction:#2' >> set_ftrace_filter Would specify that we generate two trace entries of btrfs_join_transaction(), then stop tracing this function. - Using function-triggered tracing: a function could be specified (via a filter format extension) to act as a 'start tracing' trigger. Another extension would be 'stop tracing' trigger. For example: echo 'btrfs_join_transaction:+' >> set_ftrace_filter echo 'btrfs_commit_transaction:-' >> set_ftrace_filter The '+' is a start-tracing trigger condition, the '-' is a stop-tracing trigger condition. All function calls between btrfs_join_transaction() and btrfs_commit_transaction() would be traced. The two could be combined - to generate the trace of a single btrfs transaction, one could do: echo 0 > tracing_enabled echo 'btrfs_join_transaction:+#1' >> set_ftrace_filter echo 'btrfs_commit_transaction:-#1' >> set_ftrace_filter echo 1 > tracing_enabled Other extensions are possible too: - Trace length triggers. For example one could do: echo 'btrfs_join_transaction:+*#10' >> set_ftrace_filter To trace 10 function calls [allowed by current filter settings] after the first btrfs_join_transaction() call - and stop tracing after those 10 trace entries. This would allow the creation of "surgical" one-time traces - of events and functions one is specifically interested in. Ingo -- 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/