From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754397AbYLTC4z (ORCPT ); Fri, 19 Dec 2008 21:56:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751421AbYLTC4q (ORCPT ); Fri, 19 Dec 2008 21:56:46 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:50127 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751167AbYLTC4q (ORCPT ); Fri, 19 Dec 2008 21:56:46 -0500 Date: Fri, 19 Dec 2008 21:56:44 -0500 (EST) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Pekka Paalanen cc: Ingo Molnar , =?ISO-8859-15?Q?Fr=E9d=E9ric_Weisbecker?= , Pekka J Enberg , LKML , Markus Metzger Subject: Re: ftrace behaviour (was: [PATCH] ftrace: introduce tracing_reset_online_cpus() helper) In-Reply-To: <20081220043210.40758f36@daedalus.pq.iki.fi> Message-ID: References: <20081220004453.50aec846@daedalus.pq.iki.fi> <20081219225717.GK13409@elte.hu> <20081219233443.GC17984@elte.hu> <20081220033822.362bc88a@daedalus.pq.iki.fi> <20081220043210.40758f36@daedalus.pq.iki.fi> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) 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 On Sat, 20 Dec 2008, Pekka Paalanen wrote: > > > > To implement this at the ftrace level should be a trivial change. I'm just > > saying that doing this at the "ring buffer" level might be a bit more > > complex. The ring buffer has no idea of ftrace. It should not. It is at > > a lower lever than ftrace. Although, I do think some of the protecting > > that is done at the tracing level during resize should be moved down into > > the ring buffer layer. > > Aah, so you are saying that the buffer_size file (or whatever it was called) > is part of the ring buffer user API, and not tracing user API? Nope, the buffer_size is part of the ftrace API. It was just that it seemed that Ingo was pushing that the ring buffer API should handle it. I may have misunderstood Ingo though. Note, when Ingo and I start going back and forth, we sometimes are at the implementation level, and probably will confuse the users ;-) Since the buffer_size is at the ftrace level, it will make it easier to do the changes there. > > But the ring buffer is just a buffer, is it meaningful to adjust a ring > buffer size? I cannot tell tracing to go use a different buffer. And if > there will be other users of ring buffers, they would probably want to > have their own control over the buffer size. Exactly. > > As a user, I want to adjust *the* tracing ring buffer size, not some ring > buffer size. Correct, and that is what you are doing. > > Am I making any sense? I'm trying to say that in my opinion, the > buffer_size file does not belong to the "ring buffer" level. The upper > levels should decide whether and how it offers buffer resizing. The "buffer_size" file is part of ftrace, not the ring buffer. You are making perfect sense. -- Steve