From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757168AbYLaWI2 (ORCPT ); Wed, 31 Dec 2008 17:08:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752326AbYLaWIU (ORCPT ); Wed, 31 Dec 2008 17:08:20 -0500 Received: from nf-out-0910.google.com ([64.233.182.191]:46141 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751191AbYLaWIT (ORCPT ); Wed, 31 Dec 2008 17:08:19 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:in-reply-to:references :x-mailer:mime-version:content-type:content-transfer-encoding; b=geaaaV/T1lJmtDvqrnkhFogVEa9phSMEzL6abRKXAe0zgP/uNdmsZCboI5wKRMP5ZN /JJuJqhM+s7GIo98sto4MtYBuG+Hklyx2040pZAviVMgLgFSqhH67WcF3dN0ye2NloJb 7MjNicFHmunYDugZFCsrwpL90qPrbf9P3to2Y= Date: Thu, 1 Jan 2009 00:08:12 +0200 From: Pekka Paalanen To: Steven Rostedt Cc: =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Pekka J Enberg , mingo@elte.hu, linux-kernel@vger.kernel.org, Markus Metzger Subject: Re: ftrace behaviour (was: [PATCH] ftrace: introduce tracing_reset_online_cpus() helper) Message-ID: <20090101000812.1fd2c088@iki.fi> In-Reply-To: References: <20081220004453.50aec846@daedalus.pq.iki.fi> <20081220041759.5a026f5a@daedalus.pq.iki.fi> <20081231155325.392699d0@iki.fi> <20081231205708.4ee8b141@iki.fi> X-Mailer: Claws Mail 3.6.1 (GTK+ 2.12.11; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 31 Dec 2008 14:06:26 -0500 (EST) Steven Rostedt wrote: > I was thinking of only changing the debugfs file. > > > Are we controlling an action (recording events), a feature (a buffer > > where to record) or an implementation (a ring buffer)? > > Good point. It only disables the recording, so perhaps a "record_enabled" > would be better? To me "record" sounds more of a noun than a verb, but it's both and I'm not a native speaker. Still, it brings me to "recording_enabled", and do we really need the "_enabled" part? So we end up to what I suggested earlier: "recording" with values 0 and 1. :-) Anyway, it's good to start the file name with a few distinct letters, it makes tab-completion so much easier on the command line. > > What does the user actually want to control? A buffer? A ring > > buffer? Recording stuff? The tracer? Tracing? Data flow? > > Assuming there are also other users than tracing, does it make > > sense to control the ring buffer facility itself? > > I think the name record_enabled for debugfs is the best. This is exactly > what happens (not how it is implemented). When someone echos 0 to > record_enabled (currently called tracing_on), it stops the recording, and > nothing else. The tracers still try to write to the buffer, but the write > always fails. This does not disable the tracers or even notify the tracer > that the buffers have stopped recording. This is just a simple light > weight way to stop and start recording to the trace buffers from either > user space or kernel space. Kernel space can stop it, and user space can > start it again (that was the original request for this feature). > > I'm leaning towards record_enabled now. -- Pekka Paalanen http://www.iki.fi/pq/