From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754688Ab0CWIFp (ORCPT ); Tue, 23 Mar 2010 04:05:45 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:50719 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752315Ab0CWIFm (ORCPT ); Tue, 23 Mar 2010 04:05:42 -0400 Date: Tue, 23 Mar 2010 09:05:26 +0100 From: Ingo Molnar To: Theodore Tso Cc: Frederic Weisbecker , Jan Kara , Steven Rostedt , Thomas Gleixner , Li Zefan , Peter Zijlstra , Masami Hiramatsu , Mathieu Desnoyers , LKML Subject: Re: [PATCH 0/18] Allow different tracers to be compiled independently Message-ID: <20100323080526.GB4848@elte.hu> References: <1269304340-25372-1-git-send-email-jack@suse.cz> <20100323010419.GA8292@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 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 * Theodore Tso wrote: > > On Mar 22, 2010, at 9:04 PM, Frederic Weisbecker wrote: > > > > I don't know. Yeah this first looks like a good idea but once > > CONFIG_EVENT_TRACING is enabled, each tracepoint is a lightweight thing > > and induce a tiny overhead, probably hard to notice, and this is going to > > be even more the case after the jmp label optimization patches. > > > > I liked the fact we had a general tracing kernel once the above config is > > selected. And we don't bother telling people that to use tool X you need > > CONFIG_EVENT_Y, and you need to rebuild your kernel, etc... > > Indeed, a lot of the value of tracepoints goes away if people are compiling > kernels without them and we need to get a special "tracing kernel" installed > before we can debug a problem. > > So I'd hope we can do the necessary optimization work so people don't feel > it's necessary to enable or disable tracepoints by subsystem.... Yeah, agreed. Ultra-embedded can disable them all, but other than that i think we should not make it too finegrained as a lot of tooling value is in the 'critical mass' that tracepoints have achieved. The power events tracepoints are most useful when combined with scheduling events, etc. Ingo